As ad tracking technology has developed there are a variety of features which different trackers offer.
A brief review follows, to enable you to pick the features which are appropriate for your needs.
Note: There's a more comprehensive report in the free ebook Ad Tracking SuperTips
We start first with an important distinction between the two types of tracker.
This is explained in detail here, but for a quick summary
The basic tracker can provide the following information about each hit : users IP address, browser type, operating system, date and time of click, referring Url.
You may require a tracker which can record the 'actions' of your visitor such as making a sale or downloading a book.
More advanced trackers can monitor your visitor's movements throughout your site and even after leaving your site.
If you run many campaigns then an overall summary of all of your current, expired, and scheduled ads is a useful feature.
Automatic checking of your links is possible.
Sub-campaigns allow you to provide a different Url for every advertising source but only need create the one tracking Url.
All programs allow you to view stats online.
They may differ in the extent or detail of reports, for example some may report on the total clicks for each hour period.
Reports can show the campaigns which generate the most visitors and, in the case where action tracking is available, the most sales, subscribers, downloads, etc.
Some programs can email you the stats on a daily basis.
Exporting of report stats, e.g. to a spreadsheet file, is possible.
If the supplier provides an affiliate program then you can join to earn commission on sales of the product. Owning the product that you promote always gives that extra advantage: for example you can give an explanation of how you use it or a personal testimonial as to how it has benefited you.
Check if there is a money-back guarantee or a trial period.
Some suppliers also offer a demo.
Split run testing: allows you to accurately determine the best response to, for example, different sales pages.
Sub users: allows you to provide a tracking service for others.
The major ad trackers are reviewed here