Many blogs and websites try to hide their advertisements in corners or down at the bottom of the page. Let's think for a second, how does this help you? How is that any different from just not putting up ads in the first place? If readers aren't going to see your ads, how will you make money?
Your adsense ads should be part of your page, and in areas that will cause people to read them in search of whatever they happen to be looking for in the first place when they came to your site.
When you do move beyond adsense and put up links for specific products, go all out and make a short description page for the product or make a post or write a description beneath the ad or contact the product owner for graphics or do whatever you can think of to make the ad more visible for your audience. Don't just slap the ad in front of their faces, but actually give them a reason to click in the first place!
That being said, your ad should never interfere with readers getting to your content. I highly disagree with using in text ads that are automatically generated or pop ups that appear when mousing over a section of the site because they ruin the surfing experience of your users.