Remembering to keep an open mind to new ideas and concepts, testing them, and ensuring that I keep a mental note of both "do more of that" when they work and "not even if hell freezes over" when they don't (except when google changes something).

Submission to directories in general used to be seen as the big way to promote a site, these days however (as has been said by many) generating back links needs to be a bit more thought out than just blasting out submissions. I have used IBP and WebCEO in the past with success, but actual traffic and link juice gained is very nominal.

Personally, once submitted to the major SE's - Google/Bing/Yahoo etc, I would spend the time/money on specific link mining and building instead.