The most important thing is to take action! Once you've setup your site or your campaign, the key is to get enough traffic. The more traffic you can get, the higher your the chances are to get sales.
There are many free forums out there where you can read up on affiliate promotion. You can also sign up for Clickbank's own training course, Clickbank University 2.0.
Whichever way you decide, the key is to take action!