Oh and regarding networks, I would find your niche or at least general product category 1st because some networks may be focused more in certain areas.
But in general CJ is the biggest -
Share Results Affiliate Network - Best Affiliate Program Alternative for Ecommerce Merchants looking for Quality Affiliates one of our clients has some really great programs including lots of very cool mom/family/kid products type sites. Another great network is
shareasale.com.
BUT if your niche is one that a pay per lead or B2b or CPA type offer may be a good match for then there may be other networks I would recommend for certain specific things.
NETWORK WARNING - Just a thought, I've never preached this before but seems like a good idea right now.
If you join CJ for instance BEFORE you find a niche I think your eyes could glaze over like a kid in a candy store. I think the 2000 affiliate programs there could dazzle you and get you all confused. Heck I know better and every time I go in there I waste time thinking wow thats cool - hey I could market that, or that, or that.
Realize too if they are in any of the major networks lots of pros are already promoting the program. That's why I say 1st find your niche and then find the best affiliate program, which may not even be on a network but may be an in-house program with less competition.