There are numerous repositories to source affiliate products and services from. However, some of the biggest are sites like Clickbank, Commission Junction, LinkShare and JVZoo. You'll need to go through an application process, for the most part, to get approved to sell certain products, services or digital information products. Once approved, be prepared to hustle.
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.