check out the topic on my site. I go into decent amount of detail on letters and even have a sample letter http://lancesautograph.webs.com/myletters.html

Thanks for the replies everyone! I sent out my first batch the other day, and they basically followed those rules! Thanks a lot!

Hi/Hello/Hey/Dear __________.

(short intro paragraph - my name, fave movies/songs by that person or whatever)

(any other stuff, and then saying 'I have enclosed pictures for you to sign. If you are able to sign these pictures, which I would greatly appreciate, here is my address:
...'. If you've enclosed an SASE, then you don't NEED to include the address part.)

(ending)

Sincerely/Your fan,
_________.

Something like that. =D

How do you format your letters? Do you just start off with Dear Mr. xyz? Or should I put something before that? Sorry for all the questions...