My two cents.
For my articles, I put a large square adsense block (contains 4 ads) in the middle of the article. I started doing it a few months ago, and it didn't hurt my site at all. In fact, I never even receive one complaint. Most newspapers website incorporate the same style, so I think surfers are use to it.
As far as where in the article, I usually insert it in the area of the second paragraph. Many of us have become horrible readers with ADD and never make it to the end of the article, so putting ads there didn't work for me.
This has increased my stats very nicely.
Now, when I do it, I eliminate the border and use the same background color as what is on the page, so it blends in very well.
The key is that you have to offer good content to make visitors click on your articles. That's just my style. Others will advise you to create a page that doesn't answer their inquiry, so clicking the ad will be more tempting for the surfer. Maybe that works too, but my site is a content site of which I'm very proud, so I keep the content top notch.
As far as pages without articles, well, there I play it by ear. If it's a links page, I usually put it at the top. For those, "above the fold" is key at least in my experiences.
Finally, I follow the AdSense rules to the letter. If I am unsure about something, I email and ask first. If you are new to the adsense forums, here is a tip. In every forum on the net you will find many threads about webmasters being banned from AdSense. Don't even think about playing around. Too much to lose.