A. The Mitzva

1. There is a positive mitzva upon every Kohen to bless Yidden with Bircas Kohanim.1
2. Some are of the opinion that the mitzvah is fulfilled not only by the Kohanim, but also by the non Kohanim who stand silently facing the Kohanim and concentrate on receiving the bracha.2
3. Every effort should be made to come and hear Bircas Kohanim.3
4. Women are not obligated to come to shul to hear Bircas Kohanim.4 However they are included in the bracha.5
5. One should not walk out of shul at the time of Bircas Kohanim, 6 even if he already heard it that day.7

B. Bircas Kohanim of a Non-Kohen

1. A Non-Kohen should not perform regular Bircas Kohanim in shul during the tefilla.8
2. However, at other times, even though some refrain from putting their hands on children (or others) when they bless them with the traditional Bircas Kohanim, the custom is to bless them in this manner.9
3. When Kohanim raise their hands to give the bracha they have to place their hands and fingers in a way that forms five openings.10 There are many customs as to how Kohanim hold their hands.11 According to the Zohar it is improper at all times for a Kohen or a Non-Kohen to form his fingers like the Kohanim during the time of the brachos.12

C. Concentration

1. The congregation should concentrate on the blessings of the Kohanim and not get distracted.13
2. One should not look at the hands of Kohanim at the time of the brachos.14 The custom is to cover one's face with a tallis.15
3. While the Kohanim pronounce the blessing, the congregation should not recite any passukim, but should rather concentrate silently on the words of the bracha.16 However, the prayer for dreams may be recited between the brachos while the Kohanim sing.17 Some congregations have a custom whereby the Kohanim sing before every word and the congregation recite passukim printed in their siddurim.18 These passukim should be said quietly.19
4. If a person is in the middle of Shemoneh Esrei when the Kohanim pronounce Bircas Kohanim, he should stop and listen to their blessings without answering Amen.20
5. In the middle of Bircas Kohanim, one should not answer Kaddish or Kedusha from a different minyan.21

D. Face to Face

1. One requirement for Bircas Kohanim is that the Kohanim and the nation should face each other.22
2. People standing behind the Kohanim, even if they are not directly behind, but behind them toward the side, are not included in the blessing [Area A].23
3. One who sits at the front wall of the Shul would certainly be behind the Kohanim, who stand in front of the Aron (Ark). Therefore he should move in front of the Kohanim at the time of the blessing.24
4. One does not have to be exactly in front of the Kohanim.25Toward the side is also considered in front [Area C] as is the area alongside the Kohanim [Area B].26
5. Whereas a person in the front of and towards the side of the Kohanim [Area C] can face the front of shul straight ahead without the need to tilt his face directly towards them, one who is alongside the Kohanim [Area B] must turn to face the Kohanim during the blessing.27 Some Poskim hold that congregants in all areas should tilt their heads towards the Kohanim.28 6. One should not turn his face away from the Kohanim.29
7. A partition or a wall between the Kohanim and the people is still considered face to face.30
8. When necessary, even if the people are in a different room or outside shul, as long as they are in front of the Kohanim they are included in the bracha.31
9. People who are unable to be in shul (e.g., those working in the fields or those incapacitated by sickness) are included in the blessing. The Talmud refers to them as anussim.32
10. Anyone who can easily attend and stand before the Kohanim but does not do so, or who remains behind the Kohanim in shul is disregarding the bracha and cannot be included.33
11. Some say that Yidden in the diaspora where Bircas Kohanim is not pronounced daily, are included in the daily recitation of Bircas Kohanim in Eretz Yisrael.34 However most Poskim say that the bracha of Kohanim can only include Yidden in the same country.35
12. It is better not to stand on a platform (or raised bima) and be higher than the Kohanim.36

Some Dinim and Minhagim
Amen

1. The answering of 'Amen' after each of the three Bircas Kohanim is very important.37 Even if one is in the middle of Krias Shema and its brachos, one should answer Amen.38
2. The Chazan could also answer Amen on the Birchas Kohanim 39 but the minhag is not to answer Amen.40 He should also not say the prayer for dreams.41

Baruch Hu u'Baruch Shemo

3. There is a difference of opinion as to whether one should say Baruch Hu u'Baruch Shemo upon hearing the name of Hashem during Bircas Kohanim. The minhag of many is not to say it. 42

Standing

4. One of the requirements of Bircas Kohanim is standing. This only applies to the Kohanim. The congregation may sit. Nevertheless, the minhag is for everybody to stand with awe. In case of need, one may sit.43

Acknowledgement

5. It is customary for the congregation to show appreciation to the Kohanim 44 by greeting them with "Yishar Kochacha"45 - May your strength be well directed, (i.e., May you continue to be able to perform mitzvos). This should not be done until the Chazan has finished Kaddish.46

FOOTNOTES

1. See Sefer HaChinuch, mitzva 378;Orach Chaim (O.C.) 128:2. This precept is not only performed on the Biblical level in the Beis Hamikdash; even in Chutz la'Aretz, the Diaspora, it is a mitzva asei Mid'Araissa a Biblical command. See the note of the Mishna Berura to the Rema 128:44 (following the Sha'ar HaTzion 137). The Mor V'Ketzia is of the opinion that only in the Beis Hamikdash is it d'Araissa. Recitation of Bircas Kohanim outside the Beis Hamikdash was instituted by the Sages.
2. Sefer Chareidim, quoted by the Biur Halacha, introduction to Siman 128. However, the Minchas Chinuch, mitzva 378 writes that the Ritva, Succa 31b disagrees with the Chareidim.
Some explain that according to the Chareidim there is an obligation on the non-kohanim to receive the blessings of the kohanim. This is the understanding of the Minchas Chinuch (ibid);Hafla'ah, Kesuvos 24b;Sefer Hamiktzo'os, cited in Emek Bracha(Pumerantzik), Nesias Kapayim,no.7; Aruch HaShulchan 128:4,37. Others write that the Chareidim only meant that the non-kohanim fulfil a mitzva when they are blessed (mitzva kiyumis). The Chareidim, however, agrees that there is no obligation incumbent upon them (see Davar Avraham 1:31).
3. Shulchan Aruch HaRav 128:37; Biur Halacha 128:24 s.v. im. This is because if one is in the city and is able to attend the Beis HaK'nesses but does not, he shows that the brachos are not important to him.
4. The Bach 128 and Taz 128:22 write that women are not included in the kohanim's brachos. See the M.B. 128:98 in the name of the Magen Avraham that the kohanim would not recite Bircas Kohanim for only women, however, when the kohanim pronounce the blessings for men, women are included as well. Based on this, the Piskei Teshuvos 128:61establishes that women are not obligated to go to shul in order to hear the brachos.This is unlike the Minchas Chinuch mitzva 378 and Leket HaKemach Chadash 7.
5. See Magen Avraham 128:37 quoted by M.B. 128:98 that women are included in the brachos. Nevertheless, the Aruch HaShulchan 128:38 asserts that even the Bach and Taz (see previous note) agree that women receive a blessing with the men. He explains if the brachos have no effect on women, then this would detract from the men's brachos (i.e., their fathers and husbands, for a true bracha would take effect on one's entire family). Also,very often they are unable to attend shul, in which case they would be included in the brachos, see D9.
6. See Ateres Paz, Nesias Kapayim 1:7 concerning a mitzva overes - if one stays for Bircas Kohanim he will lose out on performing a different mitzva, for instance, there is a Bris Milla being performed in another room simultaneously with Bircas Kohanim. He writes that if a minyan will remain and Bircas Kohanim will still be recited, then there are opinions that permit one to leave in order to fulfil the second mitzva. The Chavas Yair (in his work Mekor Chaim) writes that this is providing that the kohanim did not begin to chant the brachos. If, however, they started the blessings it is strictly forbidden to leave the Shul. This is comparable to leaving the Beis HaK'nesses in the middle of K'rias HaTorah, the Torah reading, in which the following verse has been applied: "Ozvei Hashem yichlu", - "Those who forsake Hashem should be wiped out." (Yeshaya 1:28).
7. Kaf HaChaim 128:149.
8. Rema 128:1; M.B. 128:3, as it is written "Atem", you (the kohanim). This excludes non-kohanim (zarim). A non-kohen that recites the Birchas Kohanim violates a positive commandment.
9. The Biur Halacha 128:1 s.v. "D'zar",asks how can it be an accepted custom for one to bless another with the verses of Bircas Kohanim, for a non-kohen violates a Biblical precept if he does so? The Biur Halacha suggests that perhaps the prohibition for a non-kohen to recite Bircas Kohanim is only when their hands are spread out. Another possibility, writes the Biur Halacha is that the Sages enacted that Bircas Kohanim can only be recited during tefilla. If one were to chant the verses of Bircas Kohanim at another time it is as if he stipulated that this recital should not be reckoned a mitzva. In that case, no prohibition has been transgressed.
In all likelihood it is the latter explanation that we rely upon, for many bless their children Friday night wih their hands placed on their children's head, see Otzer HaTefillos in the name of the Yaavetz. See Be'er Moshe 4:25; Tzitz Eliezer 11:8; Yechaveh Da'as 5:14. However, see Torah Temima, Bamidbar 6:23(no. 131) who mentions that the Gra's custom when he would bestow a blessing on another was to place only one hand on the beneficiaries head . The Torah Temima contends that the Gra did so to avoid transgressing the prohibition for a non-kohen to recite Bircas Kohanim; see also Tosafos Bracha Bamidbar 6:23. Nonetheless, the Yechaveh Da'as writes that the Gra conducted himself in this manner in accordance with the Zohar and not out of concern for the prohibition for a non-kohen to recite the brachos.
10. O.C. 128:12; M.B. 128:44,45, based on the Midrash and Zohar.
11. See Piskei Teshuvos 128:38 with note 180, who brings various minhagim. See also appendix for diagrams for many of these customs.
12. Ateres Zekeinim, on the glosses/side of the Shulchan Aruch,128:12;Kaf HaChaim 128:79. The Revevos Ephraim 1:93 writes in the name of HaGaon Rav Chaim Kanievsky shlita, that this restriction only applies if one does so with his hands raised above his head. Otherwise, it is not prohibited.
13. O.C. 128:23. See Be'er Heitev 128:46 who writes that one should not learn while the Kohanim are blessing the congregation.
14. The M.B. 128:89 writes that when the Beis Hamikdash stood and the kohanim pronounced the Sheim HaMeforash, the Ineffable Name (Hashem's Name as it is written) when they blessed the Nation, the Shechina would rest on the hands of the kohanim. Therefore in those days it would have been forbidden to even glimpse at the kohanim's hands. Today,however, the restriction is only to gaze intently as this causes one not to concentrate on the brachos.Nevertheless, the prevalent custom today is to refrain from looking at the hands of the kohanim altogether. It should also be noted that the Da'as Torah 128:23 mentions that according to the Zohar, the Shechina rests on the hands of the kohanim even in our times. Consequently, this restriction would still be in force today.
15. M.B. 128:92;. The minhag is to also cover the faces of one's children. Alternatively, one can close one's eyes or look down but one should not turn one's face away from the Kohanim. See D6.
16. O.C. 128:26; M.B. 128:103. The M.B. adds that the practice to repeat the words of the bracha after the chazan is incorrect.
17. M.B. 128:172, 130:3. The Piskei Teshuvos 130:4 writes that if the kohanim started to chant the last word of the bracha, the word shalom, before one completed the prayer, he should stop his recitation and listen to the kohanim's conclusion of the bracha. He can then finish the tefilla while the chazan recites the bracha of sim shalom. His conclusion should coincide with the chazan's completion of the bracha. In this manner his tefilla will be included in the congregation's amen.
18. Rema 128:26.
19. M.B. 128:103.
20. Igros Moshe O.C. 4:21no.2; HaGaon Rav Shlomo Zalman Auerbach zt"l in Halichos Shlomo 10:3. Rav Auerbach, ibid note 18 adds that it is proper for one to pause during the amida from when the kohanim begin to recite the bracha before fulfilling the mitzva (asher kidishanu b'mitzvosav...). See also Yabia Omer O.C. 7:12;Teshuvos V'Hanhagos 1:77, 3:44.
21. Halichos Shlomo 10:4.
22. Sota 38a; O.C. 128:23. The passuk says "Amor lahem", say to them, as a person speaks with his friend, face to face.
23. O.C. 128:24; M.B. 128:93.
24. M.B. 128:95.
25. O.C. 128:24. Nevertheless, we do find authorities who were scrupulous to face the kohanim directly. This was the practice of the Chasam Sofer as quoted by Teshuvos V'Hanhagos 3:46. See there. He wants to base this practice on a novel interpretation in the Rambam. This practice is also mentioned in Orchos Rabbeinu 1:66. See however, Beis Baruch to Chayei Adam 32:145 who writes that there is no source to support this stringency. On the contrary, unless one is known to be a pious individual,one should refrain from this custom, as it has the appearance of haughtiness (yehura).This is especially so in this instance where obviously the entire congregation cannot observe this practice.
26. M.B. 128:95.
27. Biur Halacha 128:24 s.v. Aval mi'lifneihem.
28. Shulchan Aruch HaRav 128:37, According to Rambam 14:7 Tefilla.
29. Taz 128:20, mentioned by Be'er Heitev 128:42: "Those who are standing near the southern or northern wall should not turn towards the wall, rather they should face the kohanim." The Biur Halacha 128:24 s.v. Aval writes that one who is standing in front to the side should face the "east only"(west for those east of Eretz Yisrael). Presumably, he means that one should not turn towards the south or north. Therefore, the custom of some women who tilt their faces to the sides away from the Kohanim seems to be incorrect. They should rather look down or close their eyes. See C2 and footnote 15.
30. O.C. 128:24. Nevertheless, there are those that say that when possible, it is preferable not to stand behind a partition or pillar. See Likutei Halachos (Chafetz Chaim), Ein Mishpat no. 60 to Sota 38b.
31. The Biur Halacha 128:24 s.v. Im heim; The Piskei Teshuvos 128:57 explains that this is only bedi'eved, in case of difficulty or if circumstances prevent one from being inside the Shul.
32. O.C. 128:24; Whoever is an oneis is included in the kohanim's brachos. See Igros Moshe O.C. 2:31, who writes that this is only applicable to one who if he was able to, he would have come to this Shul. One who would not come in any case, however, is not included in the brachos.
33. M.B. 128:96; Biur Halacha 128:24 s.v. Im heim; Shulchan Aruch HaRav 128:37.
34. This is because Jews residing in Chutz l'Aretz, the Diaspora, are considered anussim, see D9 above, and are included in the brachos of the kohanim of Eretz Yisrael; Shela HaKodesh;Chesed L'Alafim 6; mentioned by Piskei Teshuvos 128:57. Teshuvos V'Hanhagos 1:130 brings a minhag to request and even hire a definite Kohen in Eretz Yisrael to have him in mind during Bircas Kohanim.
35. Igros Moshe O.C. 2:31; HaGaon Rav S. Z. Auerbach zt"l in Halichos Shlomo ch. 10, Davar Halacha ; Although anussim are included in the brachos, despite the fact that they cannot hear the brachos, nonetheless, that is only said when the anusim are in the same country as the kohanim. Jews of the Diaspora, however, cannot be included in the brachos of the kohanim residing in Eretz Yisrael. This is true, even if the kohen would have specific intention for a particular Jew of Chutz l'Aretz. Moreover, according to the Igros Moshe it would seem that only anussim of the same city as the kohanim are included in Bircas Kohanim.
36. This is not the preferred manner of being "face to face" with the kohanim, Ko Sivarchu, mentioned in Piskei Teshuvos 128, note 265, 273.
37. O.C. 128:13, 25; Although the M.B. 128:99 writes in the name of the Pri Megadim that the validity of the brachos is not dependent on the congregation answering amen, Igros Moshe O.C. 2:31does in fact require the response of amen in order to validate the brachos. See Mabit, Kiryas Sefer, to Hilchos Tefilla ch.14 who writes that there is a Biblical obligation to answer amen following the brachos of the kohanim, for every bracha that its obligation is of Biblical origin, necessitates responding amen on the Biblical level as well.
38. Igros Moshe O.C. 4:21. One may only answer amen to the actual Bircas Kohanim, i.e., the Biblical verses; one may not answer amen to the bracha recited before performing a mitzva. See however, Yabia Omer 8:13 who does not differentiate between amen to the bracha on the mitzva and amen to the actual brachos.
39. M.B. 128:71. Although the Shulchan Aruch, O.C. 128:13 writes that the chazan should not respond amen following the brachos, that was because the chazan might become confused and would be unable to complete chazaras hashatz, the chazan's repetition of Shemoneh Esrei. Today, inasmuch as we pray from a siddur, this is no longer a concern. It is also not considered to be a hefsek, an interruption for the chazan to respond amen for answering amen shows our acceptance of the brachos and is considered to be for the sake of tefilla.
There is a dispute as to whether the chazan may answer amen to the bracha that the kohanim recite before performing the mitzva. The M.B., ibid writes that the chazan should not respond amen, however, the Shulchan Aruch HaRav 128:31 rules that the chazan responds amen to this bracha as well.
40. The custom is for the chazan not to respond amen to any of the brachos; see Aruch HaShulchan 128:31; Kaf HaChaim 128:112; Or L'Tzion vol. 2 Nesias Kapayim ch. 8.
41. M.B. 128 :173.
42. It seems that the minhag of Ashkenazim is not to say Baruch Hu U'Baruch Shemo; see Eshel Avraham (MiBotchatch) 124; Igros Moshe O.C. 3:17; Orchos Rabbeinu vol. 1 p.66; Revevos Ephraim 1:93. The M.B. does not discuss this issue, apparently, he is also of the opinion that Baruch Hu U'Baruch Shemo is not recited.
The minhag of Sefardim, however, is to answer Baruch Hu U'Baruch Shemo, Pri Chadash, as quoted by Be'er Heitev 128:28;Birchei Yosef 128:10; Kaf HaChaim 128:87; Yechaveh Da'as 4:9, note 1; She'eiris Yosef vol.3 p.196.
43. M.B. 128:51. Some authorities write that those who are ill and the elderly, for whom it is difficult to stand, may sit because the brachos are valid even if one does not stand, Tzizt Eliezer 14:18; Yechaveh Da'as 5:15.
44. M.B. 128:60; see also Mateh Ephraim 592:11; Reshash Shevi'is 2:4.
45. See Shabbos 87a and also the last Rashi in Chumash. Some say Yeyasher, the Mateh Ephraim ibid, brings another custom to say Asher Koach or Ye'asher Koach (with an aleph instead of a yud). Asher is interpreted homoletically as Ishur, to fortify. See Yeshaya 1:17. The aleph takes the place of the yud. See R' Akiva Eiger, Gilyon HaShas, Shabbos ibid.
46. M.B. ibid. The Ateres Paz on Nesias Kapayim no. 52 writes that on Rosh Hashana the kohanim should remain in their places until after all one hundred tekios were blown and Kaddish was completed. However I have heard and seen it written that HaGaon Rav Moshe Feinstein would tell the kohanim Yeasher Koach on Rosh Hashana before the completion of the hundred kolos, even though the accepted custom is to refrain from talking until then. His reasoning was that responding Yeasher Koach demonstrates one's acceptance of the brachos; it is therefore considered a part of Bircas Kohanim and is not regarded as an interruption.