I was told by Nathaniell, on a pretty good site that I thought was legitimate, that I could enhance my existing site by adding marketing for products related to my already niche field of Kitchen Design, and get paid for it! Silly me! I thought it was somewhat curious that I could go to a company like Design Within Reach, and ask them if I could market for them, and have them pay me. I didn't see how this could work. There was some kind of program partnership that wasn't fully explained. So after much resistance I signed up with a backup email to try it out for 7 days, and see if I could learn as much as I could. 
The key is to first validate your niche by looking at search trends, analyzing the competition and making sure it’s something that can be monetized. Once you’ve got that, start building it out and producing great content. Focus on nothing but the rankings for at least 6-12 months. During this time I would advise putting nothing on the site except for maybe a simple adsense ad. Adsense is not a profitable way to go per se, but it’s an easy way to get started, plus Google must continually sniff your site in order to serve up relevant ads. Site visitors generally find adsense to be less invasive since the ads shown to them are usually relevant anyway.
They tell you that the first step in the process is to choose a niche. In my opinion, this should be pretty easy for you determine before you even decide to get started. If not, then internet marketing may not be for you. The reason I say this is due to the amount of effort required to build a profitable business from scratch. If you can’t think of one single thing that excites or interests you, then you are going to have an uphill struggle if you plan to make a go of it in affiliate marketing.