One way to optimize Adsense earnings is to look at Google Analytics data (you have to link the two but that is trivial to do). For example, look at eCPM by screen resolution to see if your ad placements are working correctly on all screen sizes. Or look at eCPM by Content Group, which will help you figure out how lucrative certain sectors are. I also keep an eye on eCPM by browser. Used to be that Internet Explorer had the highest eCPMs. Now it's Chrome.