How strict should a new keyholder be?

I am holding for the first time for my partner and I am second-guessing how strict to be. Part of me thinks I should lay down firm rules so it feels real for him. Another part worries I will overreach, get it wrong, and make him miserable in week one.

He says he wants me to be in charge, but I know I am still learning his limits. For those who have held before, did you start soft and tighten up, or set firm rules early and ease off? How did you find the balance without just guessing?