If you are wanting to test the waters of affiliate marketing - either for a bit of extra money on the side, or in an effort to be your own boss and make a living from home, on your own time - one thing you should realize is that it will be of the utmost importance that you are able to figure out how to get people to your website (after all, you will not generate many sales if you are generating no traffic!); affiliate marketing and search engine optimization are both powerful tools if used properly - but if you are wanting to get the most out of affiliate marketing, you will have to pair it with great search engine optimization!
You will want to make sure you have an understanding of what you are targeting within your when you are setting up a website; you will either want to go with a very narrow and specific target (picking a niche that you will focus on, and sticking with this throughout all the content on your website), or you will want to go very broad (exploring lots of different topics and products, and realizing that some will be misses, but that others will be hits).
Another thing you should realize is that some people use the Internet simply to search for information and knowledge about products, while others will be looking for an opportunity to buy; as you create a website that is keyword-intensive, make sure these keywords will be attracting people to your site who are ready to make a purchase, instead of attracting those who are just wanting to gather some information.
And also, realize there is no reason for you to limit yourself on your website to just your affiliate marketing, as you can also make money on your site through pay-per-click ads. As you continue to beef up the content on your website, doing so in such a way that you will rise in search engine rankings, you will be able to seriously boost your income with a nice rotation of ads that get people to click on them - and that get extra money to keep on coming your way!