there are a number of strategies and tools that you might like to employ to help find high paying keywords.

• Buy them - Finding high paying keywords for your blog is possible by yourself for free - but as with everything a few entrepreneurial types are willing to do the leg work for you to save you some time and give you a comprehensive result. One service that you might like to try to find good keywords is Top Paying Keywords.
• Trial and Error - I know this will frustrate some of you who want a nice and easy quick fix but overall it is one of the best pieces of advice I can give. Try writing on a topic - track the results - if it pays off do it again….lots. Adsense allows you to track specific pages or sections of your blog using its ‘channels’ feature - if you’re smart you’ll watch which sections of your blog are generating the highest ads by dividing your overall earnings by the number of clicks and comparing it to other channels. Keep trying new topics until you strike gold and then dig in like crazy!
• Are there Any Ads? - This is a good first question. Despite the many thousands of advertisers using Adsense there are some topics where the answer to this question is no. A simple way to check is to head to Google and do a search for the key words you’re wanting to blog about. The results page will bring up not only a list of other sites writing about that key word (they are you competitors) but on the right hand side there will be a list of ads - these are the same sorts of ads you’ll get on your site if you write on the topic. If there are ads there, it is a good sign. If there are not - maybe its worth finding another topic to write on if you’re hoping to attract ads.
• 7 Search has a list of the 100 of the top paying keywords (in their advertising program - not Adsense) at the moment. Its a bit depressing actually to see a list like this because you’d have to sell your soul somewhat in order to go with many of them. Its an interesting site to check out though.
• Also from 7 Search (and more useful) is their Keyword Suggestion Tool which gives you an idea of what people are paying per click on different tools (again this is not specifically for Adsense but it will give you an idea of what the going rates are). Find What also has a similar service.
• Google Adsense’s biggest competitor are Overture (they run the ads on Yahoo) - they offer a service where you can enter your keywords and they will not only tell you how much advertisers are paying for the words but also how many people are searching for the term. This is a very useful tool.
• Sign up for Adwords - One way of getting a feel for how much people are willing to pay per click is to sign up with Google as an advertiser yourself. It doesn’t cost much to start a mini campaign and do some research this way. You’ll get a feel for what people are bidding on different words very quickly this way.
• Word Tracker is the best tool I’ve seen to help in finding keywords that people are searching for in the major search engines. The excellent thing about Word Tracker is that they also tell you how many other sites out there are targeting the same words! This is very handy as it will stop you targeting ‘Britney Spears’ as a Keyword phrase even though its one of the most searched for keywords on the web because literally hundreds of thousands of other sites have beaten you to the punch. Word Tracker has a free version to trial it and their paying version is even better - well worth the investment.