If you want to find out the hottest searched words, go to paid WordTracker (less than $10 for one day subs.), and get the list of top 1000 (or is it 10,000?) key phrases. You can get two reports, long term, and short term, and have adult filter on/off.
Once you like a phrase, and you think you can work with it, type it into WT and see what the traffic and competition is. Get a good sense of that.
Then use WT or google to get a sense of how much people are bidding.
Also as stated, check out other affiliate programs out there.
The effort spent in the study phase would pay handsomely year after year.