I get so many followers with this pop-up that I wrote about here. Bloggers who want the same results sign up using my affiliate link and I get $20 per sign up AND I also get paid if someone clicks on the pop-up and makes a purchase even if they never read my article. I explain more in detail here but it is by far the EASIEST affiliate program to make money.
Always disclose your affiliate relationship. Most visitors will probably understand that graphic ads will lead to your getting paid, but if you write a review or use an in-text link as a recommendation, you want your readers to know that may lead to compensation as well. This ensures you retain transparency and trust with your readers, but also, it's required by the FTC's endorsement rules.