What is your experiance ? How many adsense units give best profit for you ? I heard some stories that it was better to keep like at most 2 units and 1 for link (as the best paying adverts are first anyway) but I really don't know how true they are. Any feedback would be welcome.
I would suggest you to use maximum possible - I dont find any logic in using only two units while allowed are more than that
It is all on how they fit in your page. If you have very little content than logic would tell you not to put a bunch of ads. However, use as many ads as allowed if you can integrate them into your site with lots of original content and so it does not look spammy. There is no set fast rule it all depends on how well the site is set up and how much content the site has.
People say that less ads on a page = more CPC for those ads. I haven't tested it myself, but it's something to keep in mind.
Just in case you have a blog that has a lot of posts per page, making it very long, then it is advisable to have more adsense ads showing.
It is now heard that one can place 3 Ad units,3 Link units,1 search box and 1 refferal ad unit Anyway i have tested placing only 1 ad unit in my sites.But no change in the ecpm.So I think it depends on the content
Depends on the length of your page. For shorter pages, I use one ad unit near the beginning, finishing the page off with one ad link. On longer pages I use up to three ad units - the banner-type, horizontal ad units in the middle of the page can divide it up quite nicely if properly placed, and generally result in increased clicks. Whatever looks good I say!