Keep it simple: nobody (and I've been a "somebody" at various points for many years) wants to wade through a lot of stuff.

You'll be wasting their time and your money if you include much more than this:

1} A CD or tape or whatever to demonstrate what your act sounds like

2) A relatively hype-free bio, telling who you are, what you've done. Keep it down to a single-spaced page, if at all possible. Spare the adjectives ("Devilishly handsome Joe Smith is the greatest ukulele player to emerge from the Alabama Hawaiian music scene in years..."). If you've played prestigeous gigs, have drawn big audiences, note that. And be honest: someone will be checking up on you. A good photo or two would be nice. Nothing too arty; they want to see what you look like.

3) If you have reviews, recommendations from bookers, etc., enclose them. That's where the adjectives come in.

4) Make sure there's a contact name and phone number on EVERYTHING. And package the kit neatly, but extravagant boxes and the like don't impress anybody. A color file folder would stand out without getting in the way.

Follow up in a couple of days: "Hi, this is Joe Smith. I just wanted to make sure you received my promo package, and see if there's any other information you need."

Wait a week or so before trying again; be pleasant and eager to please, but not pushy. After a couple of "strikes," take the hint, and re-apply when you have something new to say about yourself.