yeah a few drinks is fine before stage. but don't go overboard. i've jammed with people and the more they drink.. the worse they sound but the better they think they are playing.

the first stage performance for guitar i had.. was a solo at my grad show party. basically i had to play a guitar piece in front of 300 ppl my first show. and i had to do it 2 nights in a row... well the first night i bombed it. but the second night it was easier and very much better. my advice is ignore the audience if they are being negative, just completely focus on what your doing. however if your audience likes your music. that will give you positive energy to work from and you'll do great.