OPTIMIZING CTR!
Optimizing and fine tuning CTR is what really makes money for you on Google Adsense, CTR or Click Through Rate is calculated by following formula:
(Total Viewed Ads/Total Clicks on Ads) x 100 = CTR Percentage
There are 3 ways one can effectively improve your CTR and which will finally reflect on your Google Adsense earnings, these are quality of your content, ad placement and up to date statistics on which ad units work best.
1) Ad Placement

Ad placement is nearly half of the strategy (other half being the content itself), if Ad is placed at right position with quality content, there is very good chance that you will get a click out of it. Consider the following example:

In above example we have one vertical ad unit (160x600) and we have another unit (a square or 336x280) which is actually inside the content. Question yourself, which one has more likelihood of being clicked? it is definitely the ad-unit which is placed along with the content because, 1) It gives an impression that it is part of the content 2) When user is focused on the content the user develops blindness to the surrounding area.
When using Text based ads, try to blend text ads with the "Content Text", use same font, color, font-size, background color and no borders. The basic idea is to Ghillie suit up your ads like below:

Take brownish green grass as your content and your ad being the Ghillie suited man with sniper rifle, sure he didn't blend into the environment 100%, but still, he has done 90-95% of the job.
2) Quality of the Content

Quality of the content cannot be over stressed. It is the quality of your site's content gets relative ads, maintains your site's visitors and get new visitors for your site. Google Adsense use META DESCRIPTION, META KEYWORDS and TITLE tags to target ads to your content. If you have written a nice article and left its Description and Keywords empty, you may get wrong ads targeted to your content, no ads at all, poor search engine results for that page or article and waste of quality work.
3) Statistics, Numbers and Research
Statistics provide insight into ad units that earn well and ad units that don't earn very well. You can find such statistics on on Google Adsense page and you can also test performance of your own ad-units by using channels for each ad-unit, channel is like grouping ad-units for a certain location on your site that you target (for example: Left_Vertical, Inside_Content, Right_Vertical, Top_Horizontal). After some time you can see which channels are performing well for your site and help you to rethink your strategy or go for it.
