mostly what has been said, with emphasis on the promo tools - LOTS of odd sized banners turns me on
- good stats that show referring urls & update often for those of us who like to refresh it every 5 minutes
- minimum payouts less than $100 & more than once a month
- good tours that you can pull lots of info from for text ads (spelling and grammar mistakes on tours & promo tools are my pet peeve)
- hosted free sites that are updated regularly with good content & nice layout. Quite frankly, some of the stuff out there is unusable.
If I like the site & the tour, usually it's the payouts & promo stuff that is my final decision on whether or not I'll promote it.
Ponygirl