I am a big fan of testing ad units, primarily because it lets me find the best placements for a website. I think everyone looking forward to put in adunits to make money online in their sites should do it once the sites reaches 500+ visitors a day.
You should have seen this Google adsense heatmap by Google, which according to them should give you the right clicks on your site. But not every site has the same placements and the same audience, so testing and tweaking are the only ways you can increase your adsense revenue.
The Less Is More concept
I don’t know if this concept goes by any other names online, but this is one thing which has helped some of my sites increase their revenues by almost 100%. In my younger days online, I usually slap up as many ad units as Google allows on a page and wait for clicks to drop in. But time has proven that sometimes having a single ad unit will yield you more money than having 3 ad blocks.
I used the most popular ad unit, the 300×250 ad block as a single ad on a page removing all other ads and my revenue shot up by more than 100%! My theory (feel free to disagree) is that by having less adspots, you are telling Google that you are giving them the best spot and therefore be served the most contextual ads for that spot. Another reason could be that it increases the overall usability of your site by increasing time spent on your site, which in Google terms is a “good website”.
Most of the sites have this ad unit blended into the content on the right or left. I was testing a placement where it stands out on top under the title a few weeks back and it was yielding better results than having content blended into the ads.
It is always good to at least review your placements every 6 months ifyou have been getting 10 cents clicks or no clicks at all. Also Google recently released font customization on ad units, have you checked it out? What were your results?