But how can you find such words for your site? Well, the answer to that question depends a little on who you are and what you're prepared to do to get those keywords. But the general good news is that you can indeed find such words if you need them.
Of course, if you can afford such a solution, one of the best ways of getting your hands on those words would be to pay for them. There are specialized companies that do business by finding people good keywords, not only for the purpose of more AdSense revenue but for search engine optimization as well.
Such a service can be found on "Top Paying Keywords" http://www.toppayingkeywords.com/ and this is a no-brainer to getting relevant content on your site and increasing your revenue by a whole bunch quickly.
Of course, if such a solution does not work for you, you can ultimately resort to a method of personal investigation. That means you try out keywords by yourself and see which ones work better or worse for yourself.
While you might also be doing this for the first method (paying someone else to get the keywords) it would probably be better then this because you'd at least be narrowing down search to certain items.
While you're trying this make sure to keep using AdSense's 'channels' feature along the way as it can be a very good way of letting you know which sections of your site are generating income and which aren't.
Of course, you can also yield a great amount of help from AdSense's arch enemy Overture. Overture gives you the possibility of entering keywords and finding out not only how much advertisers are paying to get them on your page, but how much people are clicking on the words as well. This service can be found at: http://www.pixelfast.com/overture/
You can also try out a tool called Word Tracker http://jeremyburns.com/a/wordtracker. What this tool can do is tell you how many sites are already using the same keywords. Learn from this lesson and don't try to use the words that a lot of people are already using.
Also, a great aid may very well be found in Google itself. Search Google for any keywords you may wish to include in your pages and look at the results. The results on the left will probably be your competitors (and if they have Google AdSense ads on their page you can bet then are) while the links on the right display ads relevant to your search.
If your search doesn't yield any AdSense results then you might want to reconsider including those keywords in your site.
Make sure you don't use any dead words (words that don't get any links on AdSense other then public ads. That is probably the most important thing you should be doing.
Of course these are only a few methods of getting out of the dead zone and starting to make serious money with AdSense. If you've seen a lot of people with "not so hot" websites generating a lot of AdSense revenue, using these tips can get you right behind them (or in front if you're really smart) very fast. Although this is the case it is also very important to remember that having the highest paying words does not mean that you make the most money. You have to also consider how many times the advert is clicked on.