New to CPA marketing

Hi Guys,

I recently applied to a few CPA networks. I have a site that is getting a few hundred uniques a day, it has around 20 pages of content. There is a left hand sidebar that links to each page and the site is in a popular niche (weight loss)

I've been promoting clickbank offers with little success, I made a couple of sales , and a few cents with adsense but the conversion rate is pants so I really want to experiment with cpa offers.

As i'm new to cpa I'm thinking e-mail or zip submits would work well and I'd rather test this out first.

I've been browsing this sub forum and noticed a lot of marketers talking about setting up landing pages specifically for different cpa offers. I guess these guys are mainly using paid traffic.

Since my site is getting organic traffic I can't just set up landing pages on the fly and can't just gear the landing page towards one cpa offer (I wish I could but it would probably affect my ranking if I keep changing the wording)

I wouldn't exactly call my site an authority site, but the other pages on my site might be distracting for the user. I was wondering if there is any way to get them to stay on the homepage and click through to the offer.

Does anyone have any tips on how I can get users to fill in simple zip/e-mail submits and how I can grab their attention?

Thanks.