Jakob Nielsen is an authority on usability; “the elegance and clarity with which the interaction with a computer program or a web site is designed” (Wikipedia). His tips are always worth reading and often worth implementing into your own website(s) whenever applicable.
In his most recent newsletter, Jakob Nielsen released a list of 10 redesign recommendations that are the most likely to increase return on investment. The subjects discussed are:
1) Email Newsletters, 2) Informative Product Pages, 3) High-Quality Photography, 4) Product Differentiation and Comparisons, 5) Support for Reordering, 6) Simplified Text, 7) Catering to Seniors, 8) Gift-Giving Support, 9) Search, 10) User Testing, and a bonus tip on implementing a loyalty program.
Be sure to read Jakob’s excellent article on design priorities for increasing website profits.