Five Things to Know About Users
http://www.uie.com/articles/five_things_to_know/

Spool, Jared M.
User Interface Engineering
2002

Abstract:

Over the years, we've studied the usability of hundreds of product and web site designs. We've seen designs that were incredibly effective for users and designs that fell tremendously short. One emerging pattern in our ongoing research is that design teams that know a lot about their users are more likely to produce user experiences that are usable, effective, and pleasing.