One of the most important things IMO, if not the most, is a well run program. I have 2 tracks within 90 minutes of my house and they both have programs that dont run well at all. One of them is improving though. Then theres a third track, and this is the one where everyone goes, and I can tell why.
Dont make the racers wait, post the races and dont change them.
Also, free lunch dosent hurt either.