the more work you put into themes, the more sales
Take your time with themes, brainstorm any and all potential client wishes and put the ones you think are most important in.
Get active on the forums, be nice and make friends! These people are an invaluable help to you, and will help you grow as a designer and developer.
Think outside the box. You’ll have more fun if you do.
(I should have done this for my WordCamp presentation. Great idea!)