Let's suppose you have an "anti-virus" website where you are promoting various products that scan your computer for viruses. You could send emails out to your list that explain what viruses are, or what new viruses are out there and how you could be infected. Then, you can mention that the viruses can be removed instantly by product A and product B. At that point you will want to add your affiliate link in the email or direct the visitor to a review page of your choice.
Offline events like trade shows are highly anticipated growth opportunities for professionals in your industry. Demo your latest product at an appropriate conference and collect signups in-person. Once you're back at the office, import these signups into your contact database. Be sure to send these contacts a welcome email that confirms their opt-in to your list. (See #8 in this blog post for tips on sending welcome emails.)
Some ad platforms will ask more of your landing pages than others, when running ads. For example, AdWords is much stricter, when compared to Facebook. AdWords typically requires that you do not have a ‘thin,’ site that is designed solely to collect leads. Because of this it might be a good idea to focus on using Facebook or Twitter, to begin with.