1. Concentrating on one format of Adsense ad. The one format that worked well for the majority is the Large Rectangle (336X280). This same format have the tendency to result in higher CTR, or the click-through rates. Why choose this format out of the many you can use? Basically because the ads will look like normal web links, and people, being used to clicking on them, click these types of links. They may or may not know they are clicking on your Adsense but as long as there are clicks, then it will all be for your advantage.
2. Create a custom palette for your ads. Choose a color that will go well with the background of your site. If your site has a white background, try to use white as the color of your ad border and background. The idea to patterning the colors is to make the Adsense look like it is part of the web pages. Again, This will result to more clicks from people visiting your site.
3. Remove the Adsense from the bottom pages of your site and put them at the top. Do not try to hide your Adsense. Put them in the place where people can see them quickly. You will be amazedhow the difference between Adsense locations can make when you see your earnings.
4. Maintain links to relevant websites. If you think some sites are better off than the others, put your ads there and try to maintaining and managing them. If there is already lots of Adsense put into that certain site, put yours on top of all of them. That way visitor will see your ads first upon browsing into that site.
5. Try to automate the insertion of your Adsense code into the webpages using SSI (or server side included). Ask your web administrator if your server supports SSI or not. How do you do it? Just save your Adsense code in a text file, save it as adsense text, and upload it to the root directory of the web server. Then using SSI, call the code on other pages. This tip is a time saver especially for those who are using automatic page generators to generate pages on their website.
These are some of the tips that have worked well for some who want to generate hundreds and even thousands on their websites. It is important to know though that ads are displayed because it fits the interest of the people viewing them. So focusing on a specific topic should be your primary purpose because the displays will be especially targeted on a topic that persons will be viewing already.
Note also that there are many other Adsense sharing the same topic as you. It is best to think of making a good ad that will be somewhat different and unique than the ones already done. Every clickthrough that visitors make is a point for you so make every click count by making your Adsense something that people will definitely click on.
Tips given by those who have boosted their earnings are just guidelines they want to share with others. If they have somehow worked wonders to some, maybe it can work wonders for you too. Try them out into your ads and see the result it will bring.