Affilate programs can be a boon or a bust to your domain. When used properly they provide content and opportunity. When implemented poorly they may serve as a contaminate ruining an otherwise fine website.

How well does the affiliate program match your website?

Are you trying to sell car parts on your kittiesarefluffy.com website?

Does the affilate program have a good solid reputation?

You care about this because you want to get paid. And, you want to protect your browsers. It doesn't help you to make a few bucks and generate bad rep because an affiliate doesn't deliver product or deal well with customers.

Are the graphics and texts professional?

No point sweating blood to make your site look great just to dump a bunch of low class cheesy buttons and banners on it.