I've been gigging since 1970 since I was 12 and basically gone out twice a week for the last 41 years.
Funnily enough I only get nervous when I go to a place for the first time but everywhere else I'm totally in control.
The best advice I can give you is that a 'normal' audience contains people who don't have much clue about what they are hearing but know what they like - all I have to say is 'Karaoke'.
Obviously there will be people like you in the audience and if you can talk to them, respect them and get advice from them.
Remember, as soon as you do your first live song you become experienced and you'll be hit by the bug.
Look at me, 41 years later and I can't wait to get on stage at the weekends so learn from your first live song and move forward.
You've also got to look at your first performance like X-Factor, in other words you've got one song to impress the audience so is Pearl Jam the very best song you can choose because I have Pearl Jam albums but I haven't got a clue what that one is?
If you enjoy it, they'll enjoy it.