I definitely think one of the keys for new affiliates starting out is to really research what your competitors are doing (other affiliates) and see where you can fill in a void that is not being tapped.
In the poker niche, there are hundreds if not thousands of affiliates targeting bonus code type terms, but there are thousands of other keywords and terms that have very little competition that can drive some serious traffic to your site. Look for those terms. Think a bit outside the box and what people might type in. Use your own mind to determine keywords and then reinforce that research with your own keyword research.
Read player forums and really see what questions people have rather than looking just at what other keywords affiliates are targeting.
Mark