on my first public performance i was playing you shook me all night long, by ac/dc and i couldnt play because i was really nervous, and didnt learn the solo good enough, so the most important thing as it seems to me when you are playing before crowd you should learn your part, as if your life depend on it, because otherwise you can find yourself in position when you are nervous, and dont remember your part, while if you'll work really good on it you'll be able to play it because your finger will just lead you to the right thing, even if your brain wont...
if you playing more than 1 song you should start with the easiest and leave the hardest to the end, because in the begining people tend to be most nervous, and dont choose songs that you are not able to play very good, in the rehearses because it will sound like crap live....

anyway remember , especialy when playing original stuff, people dont know how it should sound, most of the people will think you are good, doesnt matter what will you do...
even if you'll stop in the middle by some reason pretend that it should happen, and it is part of the song