Diversifying is the key. Go with long-term established companies that offer computer tracking affiliation. The more revenue streams you have built into your website from reliable sources, the more money your website will make for you. The best I have found that offers the most revenue streams built into their websites is www.abcdesignstudio.com. They use Google Adsense, Amazon, Commission Junction, Clickbank, Liveperson, and many others and they also provide marketing to help you even more with your website business. I would go with a company that knows what they are doing as opposed to trying to just pick one affiliate to work with. You definitely need a website that has the code already built for you in order to do this right. I hope this helps.
There are probably too many people who start trying to make money on the internet by promoting "make money on the internet" programs, it's a highly competitive subject for which it's not easy to get search ranking, consider a more specialized niche in which you can more easily get decent search ranking, buyers in some other fields are less jaded about affiliate offers and easier to sell as well.
Ideally you would write about a subject for which you have a passion, which would give you a better chance of having the motivation to make a sustained effort.
I use Commission Junction
I like to get involved with affiliate marketing and have found two programs that are both promising. The first affiliate program is Site Build It!, they are accredited by The University of Arizona, Penn State, The Citadel and other colleges. On the other hand the other affiliate program is Wealthy Affiliate University, an online university that offers a 10 day free trial. Which shall I choose?