I personally don't think filtering any ads is good for your earnings. (See my blog post for more on this: http://www.admoolah.com/blog/index.php/2005/09/blocking-low-paying-ads/) There really is no way to know which ad is low paying. If you have a click tracker like AdLogger installed, and you happen to be able to match up a click in AdLogger with a single click on some channel in AdSense, I guess you could get the amount of some single clicks. But, if you are getting so few clicks that you can track individual ones, you got bigger things to worry about than the amount per click of individual ads
it is really hard to say, you can try to search the keywords by google, if there many ads, then it maybe a high pay keywords.
I think you if you filter a Ad think that they are the low paying advertiser, you will get another ad as a substitude. And What that means, it will replace with another low paying Ad.. Repeat the loop and its an never ending process.