There is no question that you can make some good money with Google AdSense, but please avoid mistakes and follow these tips:
1. Don't "beg for clicks" or provide any incentive for clicking on your
Google AdSense ads. This is a biggie and you see this rule violated all the time.
2. Never click on the ads running on your own site, even if you are genuinely interested in the product or service and are thinking of buying it! It is not permitted to you any time.
3. Do not use fake information when opening your Google AdSense account. They will cancel your account and keep all the money you may have earned. Besides, trying to hide your true identity can cause serious problems with the I.R.S. or whoever your tax authority is.
4. Do not display AdSense ads and a competitor's ads (like Overture's) on the same page at the same time. That just makes plain good sense. Google doesn’t demand 100% SITE loyalty from you, but they do insist that their own ads not be cluttered up by offerings from their competitors.
5. Do not hack or modify
Google AdSense code other than to change the parameters that Google authorizes you to change.
6. Keep AdSense ads off of your registration, confirmation, and all "thank you" pages. Don’t ask why you can’t put your ads there. Google thinks otherwise, however, and doing so is a hanging offense according to their Terms of Service.
7. Don’t advertise anything on Google’s prohibited items list. It’s a lot shorter lists than PayPal’s or eBay’s, but it includes a lot of the same stuff like hacking/cracking content, porn, illegal drugs, gambling sites, beer or hard alcohol (I guess wine is OK), weapons, and the other usual stuff.
8. No misleading labeling Google is very specific about what text can be placed around their ads. Their Terms of Service state: “Publishers may not label the ads with text other than ‘sponsored links’ or ‘advertisements.’ See their Program Policies for details.
9. And the most Important is be honest with Google.