well for a detailed version of what you can do and can't do, better check the official Google adsense site for their terms of use. No one can explain it you better than the Google itself.
Reading the TOS is like reading a law book. Its open to interpretation. What is "cheating"? Not going to my website myself? Not inviting people to my website? What about placing ads close to each other, is that cheating, or good marketing?