Google, google, google.
Whoever figures google out with 100% accuracy should write a book for instant riches. But that’ll never happen because it’s a constantly moving target as the search engines tweak their algos trying to deliver the most relevant results, only to have their efforts exploited by clever black hatters.
Check out webmasterworld.com. There are thousands of threads there where thousands of webmasters conjecture, contradict and guess, guess, guess what the holy grail for ranking well in google is.
As far as ranking for a poker term on a non-poker site, you’re probably linking to a poker site. Linking to quality sites can improve your rankings. It shows google that your site recognizes a quality site.