Higher Paying Topics
I have found that certain Topics or I should say Keywords bring better Ads. By "better" I mean they pay more. It is not always the case, but 7 our of 10 times it is true. For instance if you have a site that talks about "games" you are going to find clicks low because generally Adsense Advertisers will only pay $0.01 to $0.02 per click. Maybe if you are lucky you get a little more: $0.05 to $0.09. Music, movies, comics and anything that attracts more entertainment always seems to be low. Such sites can benefit more from traffic though because if you have many people from across the globe checking for entertainment on your site the more likely you will have more people clicking on the Ads since they are of course related.
Sites that contain financial, legal or medical importance are usually the high paying ones. I call these "Topics That Matter" (TTM) because usually they center around things important to living unlike Entertainment. If you have a site that constantly drifts with info it is always best to make sure you highlight the TTM as much as possible each day so that SEO is catered for and you get better Ads. Of course, you will not always be able to do this, but it is good to have spare content handy. For instance I like to use Archived Topics occasionally to bring out more of a theme that may be lacking.
Feel free to talk about what works for you on your site.