Try to write one good post about an expensive product or a list of expensive products that you recommend and actually use. Make sure it has good SEO and wait about 6 months for it to start making money. This is what started making me money at first. My Non-toxic play mats posts got on the first page of Google results and it started making me affiliate income.
I personally prefer to do it that way--you can create a more convincing review that's more likely to make sales. It's not always possible or practical, though; for example, would you break up with your significant other just to test a product for getting your ex back? ;-) In cases like that, or if the product is expensive, it's usually best just to use the vendor's affiliate resources instead.
What are the terms of the program? Is there anything I need to be aware of that would make a program not worth it for me. For example, Amazon Associates does not allow you to put your affiliate links in emails. If your main method of communication with your audience is via email, Amazon might not be a good fit for you. Wayfair, for example, does not allow their affiliates to post affiliate links on Pinterest or any other social media site. If that’s a strategy you rely on, Wayfair might not be a good fit for you.
Building trust with your audience is paramount in affiliate marketing, and the quickest way to lose trust is to recommend products either you haven’t used before or that aren’t a good fit for your audience. Also make sure you never tell anyone to directly buy a product, you are simply recommending the product. The more helpful you are and the more you make quality recommendations, the more likely your web visitors will come back for your expertise.