One of the ways that people are making money with Amazon is just by the cookies. I believe Amazon is a 7-day tracking cookie, so what this means is that if a user clicks on your affiliate link to Amazon if that user makes a purchase from Amazon in the next 7 days, you get credit. Of course the game is "who helped me last" so it's whoever planted the Amazon cookie on that user's browser most recently will get the affiliate payment.

A potential strategy for monetization if you have a lot of return visitors is to just send them to Amazon as much as possible with your tracking cookie. It doesn't even have to be something like "buy this product I just reviewed here, now". Just a "check this random page out" and some of your users will likely make a purchase within a week without having your cookie overwritten, and boom you get a nice affiliate fee.

There is obviously a broad spectrum of how to send people to Amazon, and how to ethically get credit for that. But fundamentally it just comes down to having a user click through and get that cookie set.

eBay is a similar cookie game.

I'm not sure about other affiliate programs/networks. It'll be interesting to see if Google uses a similar cookie approach with their CPA AdSense ads. One would hope.