I've seen a lot of people saying they get a lot of traffic, but are unable to successful monetize this traffic. I tried and tested all these tips and they have all helped me increase my monthly paycheck from Google.
Blend Ads With Layout
Set the ad colors to match the colors of your background, link and text colors. By blending the ads, visitors won't ignore the ads and identify them
as ads. This is the best!
Don't count these out. They tend to get good clickthrough rate (CTR) because they are better at drawing a visitor in. I see to many sites that limit themselves to just text, but try switching the ad unit to show both.
Place Ads Close To The Main Content
Visitors tend to ignore ads on the sidebar and header. By placing an ad near the primary content, visitors will be more inclined to click because they will not ignore the ad. This tip has lead to the greatest increase in money from adsense.
Large Box Ads
The squarish rectangle ads like Medium Rectangle and Large Rectangle tend to have higher eCPM rates. Unlike smaller ads, these have the ability to also show image ads as well. Ads like skyscraper don't conform to content well, and don't receive high eCPM's.
Google allows you to identify the most relevant content to generate ads from of each web page by placing html snippets into the web page.
To test each ad units effectiveness, create a channel for each ad size, this way you can identify which ad unit generate the most clicks on your site. You will easily be able to tell if the banner ads generate more money than the vertical banner ads.
Google allows you to place Firefox referral ads on your site and you get I believe a $1 for each download. This is pretty easy money. This ad though is relevant to only to IE users because Firefox users already have Firefox.
There is a trick so that only IE users will see this ad...