-I go to Amazon and find a little niche category. I set up a site "buy___.com/net/org"
-I build a super simple review site for the top 10 or 20 selling items in that niche from Amazon. I get real reviews from real people and give the whole site a very personal feel.
-At the bottom or within each review article for each niche product, of course I put my "buy now from amazon" button/link.
As far as SEO goes, use each of my review articles (spun or new ones) on a few different article sites. Spread the site link around to a few forums, blogs, etc. All white hat stuff, nothing spammy.