What kind of commission do they offer? One-time commissions or recurring commissions? For example, many programs pay you one time for sending a customer. On the other hand, some programs like membership sites or SaaS (software as a service) programs will pay you a commission as long as the person you referred is a paying customer. Recurring commissions are great when you can find them!
Some commentators originally suggested that affiliate links work best in the context of the information contained within the website itself. For instance, if a website contains information pertaining to publishing a website, an affiliate link leading to a merchant's internet service provider (ISP) within that website's content would be appropriate. If a website contains information pertaining to sports, an affiliate link leading to a sporting goods website may work well within the context of the articles and information about sports. The goal, in this case, is to publish quality information on the website and provide context-oriented links to related merchant's websites.
Clickbank, huh... now that's a name I haven't heard in a while! I remember messing around with them back in 2011 when I was a newbie. Never did make any money with them, haha, but I've seen plenty of people who have! I've just never been any good at pushing the weight loss stuff, which I'm pretty sure is where most people make their money with Clickbank.
When promoting affiliate offers, just make sure you are fully aware of all the terms and conditions attached to your affiliate program. Some programs can be strict about how they allow you to promote their products. For example, some may limit you to banner ads and links only, while others will allow you to use paid advertising, but won't allow email marketing.