My favorites are:
1. Don’t start a company unless its an obsession and something you love.
2. If you have an exit strategy, its not an obsession.
4. Sales Cures All. Know how your company will make money and how you will actually make sales. (emphasis mine)
He also links to a post, How to Save Money Running a Startup, by Jason Calacanis that has some really good tips for cost control that can be used by an existing small business, not just a start-up. Be sure to read the comments too for some other good ideas.