You may have heard of ClickBank, one of the oldest and most popular affiliate networks. A billion-dollar company, ClickBank specializes in digital products like e-books and software, as well as membership sites. If you are comfortable selling information and don’t want the management and administration hassles of “real” businesses, this may be a good starting point. Its commissions can be anywhere from 10% all the way to 75%.
On one hand, long and ugly affiliate tracking links are a straight giveaway to people that you want to sell them a product (and people may be uncomfortable clicking on them). Therefore, making your link shorter and "nicer" looking will it give a more professional appearance. One of my favorite plugins for making links look "pretty" is the Pretty Links WordPress plugin.
The concept of affiliate marketing on the Internet was conceived of, put into practice and patented by William J. Tobin, the founder of PC Flowers & Gifts. Launched on the Prodigy Network in 1989, PC Flowers & Gifts remained on the service until 1996. By 1993, PC Flowers & Gifts generated sales in excess of $6 million per year on the Prodigy service. In 1998, PC Flowers and Gifts developed the business model of paying a commission on sales to the Prodigy Network.