I think it is allowed to place ( AdSense units only) 3 banner adverts, 2 link advert units and 2 search engines per page.
You can have other advertising services as well, but only the ones that doesn't look like AdSense ( visually).
Limit popups, slider adverts, popunders as well.
I think only 2 iframes are allowed as well.
For the best result add less scripts and more text, AdSense hates pages with no content.
I hope this helps.