I own 30+ domains but only have 2-3 sites that are making any money right now; the rest are setup on hosting but have nothing on them. I've also let a few dozen expire after testing a variety of tactics. One is a single-page static site that promotes a $7 item that people buy multiples of (during one month out of the year people sometimes buy 30-40 of them at a time). My second site targets kitchen products in the $50-300 range. I have custom designs on both sites. The second site is built on Wordpress with a TwentyEleven child theme that I created. I integrated a lot of things that I found by analyzing the competition and by looking at sites like consumer reports to see where they place page elements and then correlate that to heatmap studies that I've read.
I start sites with TwentyEleven as the theme and then write 3 lengthy product review pages and then build out 3-5 informational or howto pages to support the money pages. I submit the sites to pingler and stumbleupon; that's it for links. In the sidebar I add a popular products section and then a few images that link to the internal pages followed by the required affiliate disclosure. For plugins I just install Yoast SEO, Statcounter, and Widget Logic. I use Widget Logic so that I have different sidebars for each of the money pages where I put an "At a Glance" box with a rating, specs, a link to relevant things such as product manual PDFs, and a custom button linked to Amazon.
Once the site starts getting traffic and clickthroughs to Amazon then I spend time customizing the theme further and improving the page content. I learned that after this last update adding to pages seems to be more effective than creating new pages. Another thing I noticed is that whatever is in the top right corner of the site gets a lot of action; I've used the first widget in my sidebar to direct traffic to the pages that are either the most frequented from searches or that are the best resources I could build. I put a group of 4-5 pages there as custom buttons, watch what results from them in terms of traffic to the page and sales, and then I rotate them out for another batch of pages as I improve them. Eventually I'm hoping that through this method I can improve all of the pages to the point that they produce a regular, acceptable volume of clickthroughs to Amazon. I also have on one of my sites a plugin that logs searches that are performed on the site and then use the top searches each week to find new content to write about.
I've been involved in Amazon for about two years now and have done it mostly in spare time but now that my freelance business has gone down the tubes I'm looking to work on my Amazon sites full-time (or as near to it as possible). I've been paid out almost every month since the first payout cycle. At the beginning of the year I had a few pretty solid months but since then it's been down to $75-100/mo. Danny is right though, it all comes down to following a few basis rules and then experimenting to find your secret sauce. Thanks a bunch for this awesome thread dude!
June 2013 - 2 sites, seo, 985 clicks, 55 items shipped, 5.69% conversion,$96.69
May 2013 - 2 sites, seo, 667 clicks, 46 items shipped, 7.20% conversion, $86.86
April 2013 - 2 sites, seo, 803 clicks, 70 items shipped, 8.84% conversion, $75.09
March 2013 - 2 sites, seo, 1190 clicks, 84 items shipped, 7.48% conversion, $142.51
Feburary 2013 - 2 sites, seo, 1129 clicks, 201 items shipped, 18.42% conversion, $615.76
January 2013 - 2 sites, seo, 1227 clicks, 317 items shipped, 29.83% conversion, $1084.06
January and February were doing great and then out of nowhere I woke up to no traffic. Conversions have gone down this month as I was experimenting with Tumblr. I was able to get about 200 clicks but they didn't convert into sales. I had a hunch that it would be a fail but wanted to test it anyway.