That visitor clicked without prior incentive, and only clicked because of what he/she saw on the advert. Anything less than this organic process will often result in a click being deemed as invalid. The factors and tips below apply to most of the mainstream affiliate networks (not just Google’s Adsense).

Do not click on your own adverts

This is the biggest cause of invalid links in most cases, but the affiliate networks (especially Google) are aware of your own links. They may register as moneymaking links to start with, but Google will adjust the numbers later to factor in the times you clicked your links yourself.

Some affiliate advertising networks may punish you for repeatedly clicking your own links, and Google tells you not to do it in their Adsense agreement. But, Google is less likely to punish you for it, as it makes no difference to your Adsense earnings.

Do not allow people using your own computer to click your affiliate adverts
People using your computer will probably register under the same IP address. The Google Adsense program does not know that the person using your computer is not you. They assume that it is you, so even if someone who uses your computer has a genuine interest in your affiliate adverts, you will still not be paid for their clicks.

Do not use clicking bots to generate clicks
Of all the affiliate networks, Google have the biggest programming and tech team. They can spot a bot with consummate ease, so do not use them (even with VPN) as Google will know and cancel your account. There are companies that may offer to generate clicks in return for a share of the profits, but they are often caught out pretty quickly and it is your account that is cancelled.

Read full report at: http://www.oracleblogger.com/2013/09/how-to-protect-your-adsense-account.html