Old hands at doing business on the net know about preselling, but the newer folks do not which is why they must discover how to write compelling presell copy. Once you begin using presell copy in your affiliate promotions, be very sure you track and test for even greater results.
The most important thing to always remember is that preselling has nothing to do with writing sales copy. Yes, of course benefits matter, but never list them like benefit bullets as you would do in sales copy. You know what a story is like, and in a story you just tell it and people can see, hear, taste and smell the benefits of the product. So it should be apparent for you to have intimate knowledge about the benefits because that will make your presell stronger and more convincing. One other smart thing to do is Google preselling copy, and you can find more in-depth treatments with some good examples.
As far as doing A/B split testing on your copy, you could rewrite the entire introductory paragraph, for example. Do you know how to write for your particular niche audience? It is interesting that very powerful methods, like telling stories and using presell copy, are not seen very often which is suggestive. Did you know that it could take several months to properly optimize an ad campaign? But doing that will make that campaign so much more profitable for some time to come. It is those who are willing to do more and do what it takes that end-up with the brass ring.
You may be able to find a few actual products that purport to teach you how to write presell copy, but be careful and exercise due diligence. Research the merchant site and look for the product information that you can use in your presell content. Collect facts, figures, estimates, testimonials, etc from the main sales page to feed your research. It is up to you as to how much effort and real work you put into this. It is fine to get inspiration from other sources, but be bold and write in your own style. The only way to improve with writing is to do it, and so do not be shy about learning how to write your own presell copy, and you can become quite adept at it. You can find great information about presell copy for free on the net, so there is no excuse for failing to do this.