I have several blogs promoting all different products. The hardest thing I find about affiliate marketing is that once you’ve sold someone something you need to find a new product to sell them. I’ve found that promoting a subscription service where you sign up a customer is a great way to go. This way every time they renew or buy something you get paid. You only have to sell them this once.
Affiliate marketing allows you to recommend products and services from other companies and be paid a commission if someone buys the product as the result of your recommendation. To track which purchases happens as a result of your recommendation(s), the merchant will provide you with a special link to use when linking to their website that contains a unique referral code assigned to you. If people click that unique link, and buy the product or service within a specified timeframe (the timeframe varies depending on the merchant), you get a commission on the sale.
Sometimes, individual entrepreneurs with great products are worth a look, although you should check them out first and do some research. Entrepreneurs or companies may run their own affiliate program and you can apply directly to them to promote their products and services. Finally, Amazon is always an option as you can be an affiliate for just about any type of physical product on their network.
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.