Although it is fairly easy for an application sofware developer with very little knowledge of PHP, Javascript and HTML to quickly put a wordpress theme together, creating a GREAT theme requires a lot more thought, effort and discipline. And despite all the forum threads you may be reading, no advice is as good as that which comes from an experienced wordpress theme developer.

Jean-Baptiste Jung, is just that kind of freelance wordpress developer. He has put together a nice article on the Best Practices to adhere to when coding your wordpress theme. It is a list of Do’s and Don’t - what you should, and shouldn’t be doing and thinking about when coding your next wordpress theme.
Here is the full list of recommendations / best practices on Jean’s CatsWhoBlog site.