In general you will use a script like phpadsnew to automatically grab a banner out of a pool of your affiliates and display it. You can then track which programs are converting better and display their banner more frequently. Since your visitors' hosting needs change from visitor to visitor it is advisable that you have more than you run banners from more than one affiliate (some people are looking for VPS, some people are looking for reliability and don't care about price, some people are looking for the cheapest they can find, etc).