Well, I think the thing to do is to pick someone who's mature enough to understand that first-time sex might be awkward and not the best. You can talk about it with them ahead of time, too. It doesn't have to be a sit-down-and-get-serious kind of talk, just mention it and clear the air about that, then you'll feel less of an expectation. Unless, of course, they say, "What do you mean the first time might not be perfect? I expect you to be the best I've ever had, right away!" In which case that would be your cue to leave.
