Search for websites that will create your banner for free or for a small fee. Visit Quick Banner or Top Site Guide's Animated Banner Creator.
Create your banner ad, or have it created by a graphic designer. The three types of banners are flash, GIF and static.
Decide how you're going to pay your affiliates. Most companies pay per click, but you can pay per impression or a flat rate.
Place your banner on your website, and ask other website owners to display it on their site. Sometimes people will do a banner exchange with you.
Pay a site owner to display your banner ad.
Join a banner exchange program, such as 1800 Banner Exchange or Trade Banner Ads.