Affiliate Programs
If you're going to join an affiliate program...
Research shows that related text links and product images produce the best results. I would not recommend using banners if you want to make any sales. Related content dramatically increases the amount of money you can make. Join an affiliate program that relates to the theme of your site and place a link on every page.
Having an original and useful site will dramatically increase your sales. Pre-made sites, sites that use free content provided by the affiliate program, and sites that do nothing more than republish content from some other source don't do well.
It's a good idea to limit the amount of programs that you join. Choosing just two or three good programs will make managing your site easier and your site won't be cluttered or inconsistent.
When placing affiliate links on your site always remember: less is more. You won't make more money by crowding your site with flashy, flashing, blinky things. Use tasteful links that compliment your content, only place a few links on each page - but place them on every page.
Recommend Programs
AllPosters.com
AllPosters.com has good products (thousands of unique items), ships on time, and pays on time. If you're getting traffic to your site you can make money with this program.
Webmasters love Adsense.
