Less is more, avoid the wall of sound. You don't need to play the ENTIRE time.

Compliment something somebody else is doing. Ask what key the song is in and bust weird riffs following the triads if you know what that means.

Don't over-think writing. I usually find a cool chord and then try it in different positions with random hammer-ons until I find a feel I like, then I follow that groove.

Write lyrics about past experiences. I like telling stories in my lyrics. Then it doesn't sound manufactured.

Don't follow the notes of the song when singing. Try to harmonize with what you are playing.

Forget about your mistakes. We all make them and 90% of the time your audience doesn't notice.

Song write with acoustic guitars, you don't need distortion to figure out a chord progression.

Cover songs that people don't know but have heard once or twice from something else. It drives them insane and will keep them interested. For example: Where Is My Mind by The Pixies is commonly known to most people as that awesome song at the end of Fight Club, I play a Hard Core Logo song, A friend of mine plays I'm Nuthin by Ethan Hawke played in Reality Bites. You get the idea.