The click-thru rate for my Adsense ads is about 30% which mean every 100 readers, there will be 30 of them will click an ad. I would consider it as high because many people I know only have a click-thru rate of only 5%. which mean every 100 readers, there will be only 5 of them clicking So how should they optimize their websites ?
1. To have the same colour scheme as my website or should i say background.
2. I never add border to the ads units unless it matches over design for my website.
3. Try not to use different colour skin background for all my ads units.
4. I use same colour link for my ads and links to the rest of the website's pages, this allow ads to blend with alll my links.
To better view of what I mean, i'll show you some example.

I have enclosed Google screen shots of the recommended methods of using Adsense ads on your website. Take a look at these websites below, have you notice something in commom ?
These webmaster remove the "border".

Well, you are able to have your ads match your current website, make them look like text content. You could also have them stand out from your website. The choices are endless through the offering of various colors and templates.

After deciding what ad colors you want to use, you will need to decide where you want to place your ads on your webpages or blogs. Here is where Google again is kind enough to give users information on how to make more money with their services.
Lesson # 9 : Smart ways to make money online - Heatmap Placement