Well in addition to the post about splash pages. You will find that building an opt in/squeeze page can be highly effective when you are using custom graphics. Combine that with good ad copy and you will quickly start to see an increase in sign ups and sales.
Make sure that you are using an auto-responder such as Aweber. It’s powerful functions allow for you to get the most out of your campaigns. Promote your opt in page/squeeze page in places where you can get lots of veiwers. Remember, someone needs to see your ad as many times as possible. It’s proven that it take the average viewer to see your ad almost 7 times before they will even think about clicking on it. So utilize large member exchanges and very active traffic exchanges like Traffic Taxis, for maximum results!