I hate to echo something but this is a great time for it...experiment! Test everything. If you are running adsense on a site, TEST for:
1. Location
2. Color Scheme
3. Type/Layout (link, block, skyscraper)
If you get a lot of traffic, you might be able to change your ads every few days and compare stat's.
Some sites (some topics) lend themselves to certain layouts such as tall graphics or thin adlinks. Play around with different ad locations on the same pages. If you have more than one ad block on a page, use adsense channels to track them as separate entities.
Color scheme gets you into the "blend it vs. stick out" arguement. The best way of saying it, in my opinion, is this: The reader's eyes should land on your ad box naturally. That's why these are common in headers and footers.
Location: Again, use channels to test these. 3 ads max with adsense per page. THIS IS IMPORTANT...If you get more clicks in ads located farther down in a page, such a the 3rd ad box, then drop one higher ad box from your page.
Better Explanation:
You have three ad boxs on your page
A
B
C
The order in whcih ads are presented in terms of click-money is highest at the top. Therefore, your A box might generate $2 per click while box C might generate $0.40 based on your market. If your B and C locations are giving you the best click ratio's, then drop the A box so the higher money ads are in the B box.
Test, test, and test again. Style (type/layout), Color, and Location all make a difference.
A few typical ad locations and styles produce well such as the large ad box near the top of a page. However, whenever you take up above-the-fold space, your site has a higher potential of being viewed as a make-for-adsense site and you might have more people leave or leave and never return. This all gets into the type of site you are building.
And I'm rambling again.