When you are surfing the net and run across a website with a ton of adsense ads that are so stuffed on the page that you cannot distinguish the ads from the content, do you remain on the site? Do you trust the site? Do you go back to that site?

Look at your website from the visitor's point of view. What types of sites get you to come back? Don't be hasty in trying to get people to immediately leave your website for an adsense offer. Gain their trust, then they will listen to you and look at the ads as something that you suggest, and not as a way off of your website.

As for your ads, experiment. What fits in best with your theme? Do you need a bit of color at the bottom? Then use their banners. On the menu and around content use text ads. Also, look at other ways of monetizing your site. An Adsense account can be banned at a moments notice without an explanation. Then what?

So my advice is to build your site to entice people to trust you and come back, and not just a niche specific version of Google.

Good Luck~

If you have a site that people will be searching through already then adsense for search is not a bad idea, otherwise I'd skip it.

As for ads I'd stick to just a couple of ad units and try to blend them in. Make them look like they're part of the content, text links as a horizontal unit across the top under your header is pretty classic - makes them look like pages/categories on your site.

Try putting an ad unit within your post/content so it doesnt look so much like an ad.

And always blend the colors accordingly.

My vote will go to SURE have AdSense search engine, focus on square ads unit (worked very well with me), throw ad units in areas where get attention and blended with page content as well, DON'T overuse units, one well optimized ad unit is 100% than 3 random ones, FOCUS then FOCUS on your content as well as your SEO work, visitors from SE pays better than other sources (i.e: direct & referring) in the terms of AdSense, well, play nice and enjoy your profits