An affiliate program is what you make of it. You'll get out what you put in. If you just toss a copy of idevaffiliate or something on your server and hope for the best, you won't get much from it.
Step 1: Get affiliates. Want affiliates? Check out some affiliate marketing forums, post a little there, and talk some of them into using your program. They'll do the marketing from there. If it's a good program they will, without a doubt, tell their friends. They're a very chatty bunch, it's the nature of the business. Get a few, let them spread the word. They are chatty in the most awesome way possible.
Step 2: Culture what you've got. Listen to them, hear their feedback. Be quick to do payouts. They're always going to want more money, so you can't always listen to that part, but you can listen and react to other things - perhaps instead of a one time 50% payment they'd prefer a recurring 5% payment. Perhaps they want options in regards to that. Maybe they need custom coupon codes or assistance with banners.
Step 3: Close the sale. You can get all the traffic in the world to your site, but if you can't close the sale, every other step you took wasn't worth it.
The most important thing to remember is that serious affiliates see themselves as businesses. It's fair to call them businesses and for many it's their only source of income. You have to treat it like a business to business transaction. You can't act like they're a hobbyist promoting your site for fun because the serious ones are not hobbyists.
