Keep An Eye On Competitors
Keeping track of your key competitors within the pay per click advertising space will give you a good idea of which companies may have the motive to deplete your ad budget.
Watch Your Click-Through-Rates
Monitoring your click-through-rates is easy through PPC platforms such as AdWords and Bing. Spikes in keyword searches paired with a drop in click-through-rates may indicate someone is generating false impressions, hoping to damage your reputation and get your PPC ad disabled.
Use Geo-Location Features
Using geo-targeting is not only a best practice in the PPC industry, but it is also a pro-active measure in the fight against click fraud. Prevent IP addresses in irrelevant locations from viewing your ad altogether!
Set A Daily Click Limit
Setting a daily click limit will ensure your budget stays within control, and in the event you do become victim to click fraud, the fraudulent clicks will be stopped upon your click limit.
Use A Click Monitoring Service
Using a click monitoring service such as ClickReport.com is a pro-active measure in the battle against click fraud. Such services provide you with real-time alerts and notifications regarding suspicious click activity, optional pop-up warnings to ward off repeat clickers, and specific IP information to help you block certain users from viewing your ads in the future.