You should just go with the flow of the mood, don't do anything outrageous, like "doggy style", but I think that you should try missionary, because then he can control how quickly he is entering as...
When ever you like. I first had sex when i was 12 and I love having it. Just make sure you don't get an STD so try and sleep with the same guy as many times so you know there is a less likely chance...