Free Site And Blog Ad Placements - Where Do You Put Your Ads?

When it comes to building free sites and running your blogs, how do you decide where you are going to be putting your money making ads?

For a long time i stuck with the standard, top left, center middle and bottom right mindset however, more and more as of late im starting to switch things up with my ad placements and have noticed some interesting results, especially on blogs where im using either 125x125 or 150x150 buttons on the right hand side column of the blog.

When it comes to deciding where you place your ads on the sites you operate, do you tend to stick with the same placements across all of them or do you try to change things around a little?

Are there any ad placements you have wanted to try but havent yet or likewise, any placements you have tried that provided better results for you than what you previously did?

Regards,

Lee