Affiliate advertising is simple. You are basically doing the job that a sales staff would normally do for a customer. You bring customers to them, the customers buy their products and services, and then you get paid a commission. Pretty simple, right? Well, since affiliate advertising is totally based on the internet, the trick is to get users to the vendor's website from YOUR website(s). So, the basic truth of your affiliate advertising success is that you have to drive people to your website, who are interested in buying that vendor's product(s).
Affiliate advertising is responsible for billions of dollars in annual online sales every year. This results in millions of dollars in commissions for affiliate advertisers. So, don't expect to beat out the other guys without a fight. They are gunning to get that money as well, so you need to approach affiliate advertising with care, and plan your "attack" thoroughly.
Step number one is to get yourself signed up with one or several affiliate advertising networks. These networks negotiate contracts with vendors to sell their products at a certain price, and to get paid a certain commission off of that price. Then, the affiliate advertising network awards the affiliates who send them the traffic which result in sales by giving them a portion of the negotiated commission. Pay very close attention to each network's terms of service. Also, read each product or service that you are advertising very carefully. Usually vendors have specific rules that you must abide by when advertising their products, and breaking either "contract" can result in your getting ejected from the affiliate advertising network, forfeiting all earnings that you have not been paid as of yet.