I did come across a couple of online marketers who define their PPC campaign success to no. of clicks on the ad, click-through-rate (CTR) and cost-per-click (CPC). I definitely agree these are required to measure the performance of the PPC campaign but, do not judge the success of a PPC campaign by taking only these two factors. Many advertisers generate a large amount of clicks for their ads, but at the end you also need to note how many of these clicks have been converted to leads or sales.
So, ensure you have the following when you run the PPC campaigns -
Look at cost-per-acquisition (CPA). This will let you know average cost of each lead or download or sales that has happen. Accordingly you can compare or plan to invest in other online / offline campaigns.
Doing an analysis on the CPA number you get, try to predict the CPA at various spend levels. This helps you to reach optimal CPA.
Make the campaigns as keyword rich as possible using long-tail keywords pertaining to your business or products segregated as different groups. You can use the keyword tools provided by Adwords or WordTracker or KeywordSpy.
Each group or the set of keywords has the respective and related landing page. This will help to get a better quality score and will reduce the CPC. Not only CPC, but will also help in better conversions.
Use the geo-targeting, day-parting methods to reduce the unwanted clicks.
Try to use a back-end database or system which can track the CPC of each click and measures the ROI of each keyword.
There are many more tips and strategies that need to understand. PPC campaigns are easy to setup, but much more difficult to manage and optimize. Doing this takes time and effort. But, if you have the dedication to make the campaign a success then cheers.