How do you presell a Zip+Email CPA?

I can drive traffic to an niche adsense page, I created an ebook as well, but that's about all the IM experience I have. I'm new to Preselling, I'm new to CPA. I don't know how this stuff works and I don't want to sink money I don't have. I'd like to use vouchers (bing, FB, Adwords) until I turn a profit.

So as I understand it: Preselling can be done by garnering user trust towards the product before the actual sell. Product Reviews are presells, Authority/News articles are presells, User experiences on blogs are presells.

So the question I have is this: How the hell do I presell a zip+email submit? There aren't any product benefits you know? Can anybody offer any case studies?

How would I presell a Game/Gamestop-Coupon email offer if I'm targeting gamers? How would I presell an ipad email+zip offer if I'm targeting college kids? It's not like I can just talk about how great a free ipad would be on a FB LP right?

Thanks a lot for the time guys, I've been lurking only a short while and already learned so much.