How Not to Get Banned, Short Version:
- Never Try to Cheat the System
- Never Participate in Click-Fraud Schemes
- Do Not Edit the AdSense Code on Your Site
- Never Click Your Own Ads
Perhaps the dumbest thing anyone can do is click the ads that are appearing on your websites, or blogs. It is impossible to fool Google, so do not even think about doing it unless you just do not care. This is simply nothing to be debated or contested, so do not ever do it. It's alright if you accidently clicked on one your ads, but doing that again and again is a strict no-no.
Keep things relevant at all times and not just with Google because when you think about this it really is all about being targeted. Be very sure to keep your site content as targeted, and relevant to your market, as possible. It is only for your benefit that you keep the content on your sites highly relevant because that ensures relevant ads and increased click throughs. Google does not want you to have an Adsense farm, and that means when there are more ads than useful content. If you have very little content, then what will happen is Google can put non-targeted ads on display which does you no good.
You cannot, or should not, set and forget your Adsense account because you need to keep an eye on something called, click through rate. The standard, or average, CTR is approximately 1% to 5%, and you do need to make sure it stays somewhere around that range. A sudden and unusually high CTR simply means click fraud, and you should contact Google in that event. Even though it is not your fault, you still have to do something about it even if it is just letting Google know that something unusual is going on. Keyword stuffing is a very old practice that went the way of the dinosaurs - do not do it. It is so incredibly easy to mention any keyword roughly 1 to 3% of the time in an article, and you will be fine if you do that. Perhaps the best approach is to just naturally write your content, and it is easy to get the right keyword density if you do that. Hopefully you have a better awareness of why you simply must make sure your Adsense account is protected at all times. Google's TOS are not overly strict, it is just that so many people try to game the system in one way or another.
Make sure your sites load quickly, otherwise you will have a high bounce-rate and lower revenue. Here's a post with more information: speed up WordPress.