“10 Steps to Effective Copywriting” by Susan Gunelius (Entrepreneur Magazine, Entrepreneur.com, 16 February 2009). If you commit any of these ten to memory go for:

4 – Communicate W.I.I.F.M. (What’s In It For Me?)
5 – Focus on “you,” not “we.”
7 – Avoid T.M.I. (Too Much Information)

You’ll have to read the rest of the article if you want to get your money’s worth.