It doesn't matter how 'good' a player/singer you are. You've just got to mean it. Do what YOU like, and then you'll feel passionately about it. Fuck what anybody else says. Don't take any notice when people say, "you should have some [insert instrument] in your band", or "you want to sound more like [insert crappy NME 'style' band]". Just fucking do it. Music is your opportunity to have your voice heard, so you've got to say it in your way not someone else's. It doesn't matter what you look like. Don't feel you have to dress in a certain way, or look like a particular 'sort' of music. Just be you.