Is one permitted to cut a surgical dressing or bandage to the required size?

This is a real problem of Kore’ah [1] and possibly one of Mechatech as well. Briefly, one may not tear anything for a specific use, because the tearing is beneficial and involves an issur of tearing on Shabbos. [2] This is not to be confused with tearing a packet, which is torn in order to obtain the contents. Tearing a dressing is to enable its proper use.

Mechatech is the melacha of tearing or cutting something to a very specific size. This does not mean that every time one cuts a bandage one will be violating Mechatech as well, because often one does not need to cut to a specific, exact size.

If I cannot cut the bandage how am I to dress a wound?

If it is the type of bandage that comes as a roll, one should wrap the entire roll around the wound without cutting it, and then hold it in place with the regular clips or a safety pin. When the person being bandaged is ill, one may ask a gentile to cut the bandage to size. This is based on the halacha that one may ask a gentile to violate the Shabbos for the sake of an ill person. [3]

If I happen to buy a special fruit or a tasty pastry, must I leave it for Shabbos or may I eat it during the week?

There is a famous machlokes between Shamai Hazaken and Hillel regarding the issue of setting aside something special for Shabbos. [4] The Torah states 'zachor es yom hashabbos l'kadsho', and Shamai learns from this that one must have Shabbos in mind throughout the week. It was said about Shamai that he would constantly think about Shabbos. When he would purchase a pleasant item, he would set it aside for Shabbos. It is also said that throughout the week he would eat for Shabbos, because when he found a pleasing portion he would dedicate it for Shabbos. When he found a more pleasant item, he would eat the first one and dedicate the new one for Shabbos.

Hillel had a different outlook on life and he said 'baruch Hashem yom yom', meaning Hashem will provide what one needs for Shabbos and it is unnecessary to dedicate anything for Shabbos from the beginning of the week.

As we tend to follow Hillel, it would therefore seem from this that one need not dedicate anything for Shabbos.

Not so fast - this is not quite accurate: one needs a generous amount of bitachon – trust in Hashem in order not to have to prepare early in the week for Shabbos. The Mishna Berura writes that many poskim hold that even Hillel agrees that Shamai’s method is the preferred one, but Hillel had full trust in Hashem that Hashem would send him the best for Shabbos and in order to strengthen his trust in Hashem he would not dedicate the best for Shabbos early in the week. Regular people who do not possess such a magnitude of bitachon in Hashem must surely dedicate the best for Shabbos, even from the beginning of the week. [5]

May I buy the challos before davening on Friday morning, or only after davening?

The basis for this question is that one is not permitted to engage in any activity before davening, as the possuk states - 'tzedek l'fonov yahalech', one must not engage in activities before praying for one’s life.

However, this possuk pertains to mundane matters. One may engage in matters which involve mitzvos and honor of Hashem before davening as well.

Another important issue is that one should purchase the Shabbos needs early on Friday, as this is learned from the Manna that was gathered early in the morning. [6]

Accordingly therefore one should purchase all that one needs for Shabbos soon after davening, but if one will not find what one needs in the store for Shabbos after davening, one may purchase them before davening.

How should one go about shopping for Shabbos?

The optimal method (time permitting) is to buy the Shabbos food and treats on Friday being that it is more noticeable that it is done to honor the Shabbos. This obviously refers to the items that do not require preparation, such as fruit, candies etc. [7] When buying items for Shabbos it is correct to say 'l'kavod shabbos'  – to honor the Shabbos, so as to apply holiness to the purchased item with one’s lips. [8]

If one has servants and help, may they be sent to do the shopping and all the Shabbos preparations, or should one be personally involved as well?

We learn from the greatest Amora’im [9] that they themselves prepared something for Shabbos. Rav Chisda would prepare the salad and Rabah and Rav Yosef would chop the wood. Rav Nachman would remove all the weekday articles and prepare the Shabbos ones. One should learn from these great sages that one should be involved with the Shabbos preparations. The Mishna Berura adds [10] that this is even more important in the winter months when Friday is short and help is needed in order to finish everything on time.