The key to creating a list in any niche is to create a Squeez page, and to use the proper ad copy. Make sure your squeez fits into PPV window.
Step 1) Ad Copy
Example of ad-copy:
1) Weight Loss
"Discover the secret to get you in shape by Christmas Guaranteed"
"Discover the secret that can start making you $1,000 per day trading Forex"
Notice how the word "Discover" doesn't promise them anything free. Just an opportunity to learn more.
Step 2) Opt-in Box and Submit Button
Below the adcopy you would have your opt-in box, and a nice submit button. For submit button I like ones like "Get Access Now" , "Get Started Now" "Click Here To Continue"
Step 3) Send them to Offer
At this point you send them to an affiliate offer where they will "Discover" more from the sales page. If they don't buy at least you have them in your list, and continue to promote like type products.
If you want to get them to double opt-in, give away a free gift and direct them to there email on your thank you page to get download link from email.
I hope this little nugget can help some people.
To Your Success!