Here is the trick:
> Take some high CPC keywords: I am giving some keywords list
> Place 5-10 keywords(ex : keyword1,keyword2,keyword3...) at the end of each article in each post. ( use AdInjection plugin in wordpress >> use bottom ad in adinjection)
> Save your templates ( Clear caches if you cache plugins)
> Now Go to your site and see for which keywords u r getting relavent infold,intext ads... if you are not getting relavent ads to those added keywords change the keywords.
> Try untill u get relavent keyword ads ( usually u will get in first attempt)
> Use two intag ads(top and bottom).
P.S: Don't add keywords in the beginning. If you do like that bounce rate will go up.