The Board of Directors is the legal protectorate for the interests of all of the company's employees, customers, suppliers, creditors and shareholders. From a business standpoint, the Board is the CEO's direct supervisor and closest advisor. It should be where the CEO turns when he or she is out of answers.
Good directors are knowledgeable, calm advisors.
Calm is important, since panic at sea can cost lives, and all start-ups hit heavy weather sooner or later. Being calm in a tough spot comes from both experience and disposition. In considering Board members, the CEO should consider both of these attributes. Small boards are more effective than large ones. Start-ups suffer many disadvantages to larger competitors.