Don’t ask others to click on Google ads
Again, you'd think this was obvious, but not the the publisher I saw a few months ago with a huge 250x500 pixel image reminding visitors to click at least three ads a day, or else their free access to the site might be gone the following day.

Don’t employ pop-up prompts or automatic software installations
Sneaky pop-ups containing AdSense or reminders to click the ads have been hitting the radar recently.

Be aware of how your site is promoted
This seems to be reminding those publishers who are utilizing spyware to promote their site with AdSense ads as being against the AdSense terms and policies.

Don’t place Google ads on sites that contain prohibited content
I still see AdSense showing up on adult or gambling sites these days.

Respect Google trademarks
Reminding publishers who are utilizing Google logos etc about their brand guidelines.

Don’t tamper with the AdSense code
It is always amazing how frequently people change the java script yet don't realize it is against the AdSense terms.

Provide a positive user experience
Someone should remind the publisher who bombarded me with eight popups, a full complement of Google ads and about two sentences of keyword spam content on the page.

Provide a good environment for advertisers
About creating pages advertisers would be happy to see their ads appearing on.

Be responsive
If Google emails you with an account or policy issue, respond ASAP :)