When is the best time to shave before a hair removal procedure?

I am planning to get a hair removal treatment, but since it is my first time, I have many questions, starting from the preparation process. In particular, I am not sure when is the best time to shave before the procedure.

I am confused because when I search online, some posts say to do it a day in advance, while others say it is fine to do it on the same day. I have also seen comments saying that shaving too short is bad, and conversely, that the procedure is difficult if the hair is long, so I am wondering exactly how I should prepare.

I would also like to know in advance if there are any precautions I should take before and after the procedure. I have heard that I should avoid exercise and saunas, but I am curious to know just how careful I actually need to be. I would like to hear the experiences of those who have had hair removal treatment for the first time and how they prepared.