If these fasts past and rain didn’t come, they would lessen their business activities like building and planting, no kidushin and nissuin were done, and people would not greet each other, like people who are censured by Hashem.

Individuals would continue fasting (Mondays and Thursdays) until the end of Nissan. If rains came after Nissan, it was considered a curse.

Taanis 2:1

On public fasts there was a special way to daven. They would take out an aron kodesh to the town square. They would put ashes on top of the aron, on the head of the Nassi, and the head of the Bais Din. Everyone else would put ashes on their own head.

The elder amongst them says before them words of inspiration. They would say, ‘Brothers, it doesn’t say by the people of Ninveh that Hashem saw their fasting and sack cloth rather that they returned from their bad ways. It says rip your hearts and not your clothes.’