Nervous bedroom communicator

So I started seeing someone new and when it comes to the bedroom I can be a little shy communicating what I do and don't like. I don't want to come off as bossy or make him feel like he's doing a bad job and was wondering how you ladies tell your guy what you like. Do you tell him during sex? Before or after? Do you just put him where you want him? Please help a girl out! All tips are much appreciated!