When choosing Affiliate Products it's a good thing to keep in mind that "physical products" have a large manufacturing cost component in their pricing, so your profit margins are skinnier. So my first advice is to choose digital products such as books or online services such as dating (dating services can offer affiliate commissions up to 75% or more so if you like this field it can be very lucrative).
For more information on affiliate programs you can download my free book at: http://homebasedbusinessontheweb.com/cap/
Let's look at some places to find affiliate products. You can of course go to Google and enter the search term "affiliate products" but an easier place to start is with affiliate networks. Affiliate networks act as middlemen between merchants and affiliate marketers. Joining an affiliate network is free for affiliates and offers a large range of high quality programs to choose from. You can feel much safer about your commissions actually being paid out to you by these legitimate marketers. They are a great place to start your search because the information is tabulated for you.
Here are a few:
The three largest are: Commission Junction: http://cj.com/
"Click Bank" is a network that specializes in Digital Products. http://clickbank.com/index.html
Residual Commission Finder: http://residualincomefinder.com.
provides a comprehensive listing of merchants offering long-term commissions for customers that you bring them. They offer listings of Affiliate Programs that payout commissions for at least a year.
Let's look at Clickbank as an example since I have recommended you start with digital products. You open their site at http://clickbank.com/index.html and click on the "Become an Affiliate" link, which you will find in the left hand column. You then click on "Sign up" and fill in the simple form and "voila" you're a registered member. Once you are a member you fill in your email and password in the box at the top right of the page and login to the members area.
Then you go inside and search around the affiliate listings for programs that interest you. Just do the same with the other networks I've listed and you're on your way. There are many more affiliate networks you can check out but this will get you started. The process is quite straight forward…you'll be an old hand in no time at all.