Well you have your newly approved google Adsense account approved, you managed to build your ads and grab your code snippets, and uploaded this into your website and or blogs and all feels great. But no one is clicking! It is now time for you to start optimizing. Don't worry it will take awhile most likely to get it right and even then it can vary from one site to the next. What works for some people might vary well not work for you or your site. That said, Google's Adsense program is still one of the biggest tools a publisher has to making money by monetizing their website. It could be you have high traffic and a low click through only due to the fact your ads are not optimized enough to bring in that lucrative revenue. So why leave things to chance, experiment a little and see if any of these tips work. They've worked for others.

Some people report drastic changes in their click through rates and their revenue by just changing a few things while still keeping their overall visitors and traffic steady. Perhaps this could work for you. In the past some of these tips have worked wonders for me on other sites.

Are you using those big banners and skyscraper type ads? Many people in the Adsense community as well as many polling companies have mentioned many a time that the average surfer on the internet is becoming desensitized to ads. In short they are "blind" to them and nothing screams ADVERTISMENT like those big skyscrapers and banner types. Try not using these and see what happens. What seems to work best is when ads can be "worked" into an article, to make it flow and seem like it is part of the overall look and not some big flashy neon banner blinking away. This can be done quite easily.
Try choosing a smaller dimension format. Perhaps a 250x250 square. There are quite a few smaller ad choices that can be chosen so experiment a little. Next look at your page that this ad will be displayed on, and tweak the background color of your ad to be the same as that of the articles or the section of page the ad is sitting on. Or at least as close as possible to give the ad a feeling of "blending" in. Next get rid of those borders around the ad by setting the color as well, to that of your background or as close as possible. All of these changes are simple and quick and can be done within your Adsense account. Remember that each time you make changes the code will be given in the footer of the page in your Adsens account, so you have to paste this new javascript into your website page. Changes can take as long as 10 minutes at times to take affect. Although I've never had to wait that long myself.

Another tip often mentioned is the positioning of the ad itself. Obviously you want to place your ads somewhere that will be noticed best. I wont tell you I know exactly where that "sweet" spot is, but it has been said, and it does seem plausible, that the first place the average person looks is the top left most corner of any page, and then begin to scan to the rest of the page from that starting point. Perhaps the way the web is setup, we are trained to look there first. Most menus hang around that area, navigation as well. Even search engines place the most important information up top and first. Or at least what they think is most important anyhow. Many languages as well read from left to right , top to bottom which again seems to fit this argument. That being said most people seem to have more success the closer their ads get to the top left and less as the ads seem to migrate further down to the right. Again, this is a test and see deal.

Next up is looking at what type of Adsense ads you display. Or more exact, what type of format. So far I have been assuming the normal text box content types. Adsense has another type that are Adlinks. These create a series of links that look similar to a normal Google Adsense adverts box, that a person can click on, where they are then taken to what looks like a google search results page. I am sure you have seen these. What I like about these, is that every time the visitor clicks on one of these they go to the page that looks like a google search results page and start clicking on various links/adverts. As a publisher you get paid for each click through and if it was not what they were looking for? There is a good chance the visitor may just back arrow and try another link or two etc. which Is good for you.

Now these are only some basic tips and basic techniques that will take time to master and refine to your sites needs. But if you have noticed your clickthrough has started dropping perhaps your visitors are indeed becoming immune to your ads. Time to switch it up and give the place a new look by playing with your ads.
I should also not that the Adsense account had a section for tracking your ads statistics, that allow you to track ads, ad formats, across your site and across multiple sites to see exactly what is performing and what is not performing and where.
By spending an hour on your site/s and tweaking your ads, their formats, locations and sizes, you can have drastic results and changes. Perhaps some of these tips will work for you too!
If you have any of your own, feel free to post them and comment. Best of luck in optimizing your Adsense Ads!

For more information on Adsense, I recommend reading the following book.