Do they value and help their affiliates? Some affiliate programs do an exceptional job of communicating with their affiliates, notifying them of upcoming sales, offering marketing advice or tools, offering contents and prizes during promotions and more. These types of affiliate programs are a pleasure to be a part of. Ultimate Bundles is an excellent example.
Whether you are promoting your own products or someone else's through ClickBank, you'll want to make sure your website is functional, error-free, and sales oriented. You will also want to begin capturing visitor's information as soon as possible by offering a newsletter. This helps you build a dedicated audience to market all of your affiliate offers both now and in the future. If you still have questions about using ClickBank, check out ClickBank University. They offer free videos and tutorials that will help you get set up so you can start earning revenue.
If you have pop-ups and optins on every page, I would have to think that it would be a lot harder to convince someone to link to it. Especially since the pages where you have your optins (and probably receive the most traffic) are probably the same pages that you have your best content on as well that you'd be hoping to pitch in your outreach campaign.