If you were ready to take the next step than you wouldnt have to ask that question. Don't be immature about it because giving even just the smallest bit of yourself to someone for the wrong reasons is something you can regret. Wait till you know for sure that it's something you want to do and not something that society or your boyfriend even has placed into your head as something your suppose to do. Never do anything that will make you think less about yourself. You set your own expectations.
You should kiss your boyfriend when both of you are ready. It also depends on how much you like him and how comfortable you are with him. You should also know what kissing someone means i.e. I would like to know you more as a girlfriend/boyfriend.