How to orgasm?

My boyfriend is going to eat me out for the first time and it's his first time doing it. The couple times I had it done to me I never orgasmed. I want to orgasm this time and I have him tips of what to do. Like focusing on the clit and fingering me. Is there anything else he needs to do? Or that I need to do? Also what does it feel like during the build up and then right before?
Thanks