According to Vincent Flanders, found of the website (and book), Web Pages That Suck, the most important website design tip is to ask yourself this question: “What would Amazon do?” He then lists 5 technologies to avoid.
It’s an important question because Amazon.com has probably spent more time and money researching what works and doesn’t work on a web site than anyone. If you don’t see a web design technique on Amazon.com, you probably should follow their guidelines and not use it on your site.
Nordquist Blog 