Latest Google Adsense Policies - Google Adsense Placement of Ads

Google Adsense Policies Updated: 8 Important points regarding Google Adsense Policies & Placement

1. Don't click on your own ads.
2. Don't ask others to click on your ads.
3. Don't include any prohibited site content, including adult content, violence or excessive profanity, drugs (including alcohol and tobacco), or copyrighted material.
4. Don't modify the AdSense code.
5. Do follow our Webmaster Quality Guidelines.
6. Do provide a good user experience.
7. Don't place more than 3 ad units, 3 link units, 2 search boxes, and 3 referral units on any page.
8. Don't place images near ads in a way that may mislead users into thinking that the images are associated with the ads.

source: google.com/adsense/support