Is it better to choose small, unobtrusive ads, or should you get them as big as you can? This Google AdSense tutorial will give you an idea about what will perform better on your site.
Q: I want to place an advert inside the content. What size should I pick?
A: Normally, the biggest ad formats will perform best inside text. If there's enough room for it, pick the large rectangle, and wrap the text around it.
If you have a really large block set aside for text, you might even get nice results by adding two AdSense units of 200 x 200.
Q: Is the same answer valid for the menu? Should I add a 200 x 200 ad unit here?
A: As always, it's important to blend in your ads with your content, and in the menu you probably have links and not text.
The best choice here is to place a link unit. If your links are presented in a vertical format, choose the vertical link unit. Pick the largest possible, which will fit inside your menu.
If you have a horizontal link menu, go with the horizontal link unit as well, and as large as possible. Sometimes, you can even get great results with a large leader board here instead of a link unit.
Q: I used to have banner ads on my site. Couldn't I just replace them with the 468 x 60 unit?
A: No. It would probably be your worst choice. I have personally made some income with the 468 x 60 text unit, but that was back when it was allowed to have pictured positioned near the ad, without separating them with a significant border.
However, since people associate the 468 x 60 format with banners, and since most people are banner blind, I wouldn't recommend that you use it. You're not likely to receive many clicks on it.
Remember always to consult the AdSense policies, before you place your ads. It will tell you things like how many units, you're allowed to have on your site, and what kind of units, you can have, whether or not you can add pictures near your ads, etc.
Q: Should I add as many adverts as I'm allowed to?
A: No, not necessarily. People have reported to get better results by using only one or two units, instead of taking advantage of the full amount.
Nevertheless, you shouldn't take this as a definite answer. Test it on your site. What works on one site, doesn't necessarily work on another. Testing and tweaking are always better than to learn from second-hand knowledge.
Three Pivot Points To Make A Lot Of Cash With Google AdSense Why You Are Having Problems With Your Earnings 5 Tips To Improve Your Google AdSense Click Through Rate (CTR) PPC Campaign Management Tips for Beginners Does Google AdSense Really Work?