Professional headshots are a must. A pretty good picture your friend took of you once is not a professional headshot. Clubs, rooms, any gig – they need these photos to promote. And any comic that doesn’t have a professional headshot looks VERY amateur to a booker.
Your headshot needs to look like you. Not like you used to or an air-brushed version of you, but you. You’re being cast – don’t show up and surprise the booker by being unrecognizable. And please don’t make em zany. There’s a difference between a candid promotional shot and a headshot. Smile – or try to capture an expression that reflects your style on stage (I prefer mine to contain a slight smirk). Your headshot should just be your face (and perhaps some of your torso). And for the love of anything holy, it NEEDS to be in color. If you want a cheap place to print them, try http://www.GotPrint.com (I print almost all of my promo with them).