[Toby]

1. A leak free tour that converts
2. A member area that retains (quality content with regular updates)
3. hosted galleries and content zips, updated at least monthly
4. For solo independed sites, use of CCBill for billing.

#'s 1 & 2: Except for the leak free part, these apply more to the site in general than to the affiliate program specifically, but they are very important to both.

#3: This doesn't need to be fancy, just effective and fairly simple to use.

#4: This is personal preference, but I really like the way CCBill aggregates payments from all sponsors into one check. I don't have to wait to meet the payout minimums. I also find most of the other processor based affiliate back ends to be extremely lacking in stats. While CCBill's stats could be better they're leaps and bounds ahead of Verotel and others.

There are lots of other details too, but those are the most important to me when I'm deciding where to push my traffic. I'm signed up with hundreds of programs, but only actively push traffic to a 25 to 30.