comming from someone who books bands at places.....
dont ask for a date in a 3-day section like "the 13, 14, or 15" one month ahead of time and expect to get it.......2 to 3 months in advance is better...i'd have a good chance of getting a band in that way. especially if your an out of town or out of state band and no one has heard of you before in that general area. i also agree with sending the email first....if I have talked to you through email, then I'm more like to listen/look at your promo when i get it in the mail vs. just sending me a promo pack.
calling to confirm a date or finding out what other dates are open is also good....being flexible with when you play will get more shows. and sometimes it can get you on a better bill than just you and some other band that no one knows on a tuesday night.