Answer by Tim Westergren, Founder of Pandora:
Learn public speaking.
Of all the skills that an entrepreneur can have, I think the ability to convey an idea or opportunity, with confidence, eloquence and passion is the most universally useful skill. Whether you’re pitching a group of investors, rallying your employees, selling a customer, recruiting talent, addressing consumers, or doing a press tour, the ability to deliver a great talk is absolutely invaluable. And it is perhaps THE most under-recognized and under-nurtured skill.