About 12 years ago I was trying to learn more about personal investing. My good friend Bill Ackman, currently a hedge fund manager for Pershing Square Capital Management, told me, "Read all of Warren Buffet's Berkshire-Hathaway shareholder letters. That's all you need to know."
I've been reading them voraciously ever since. They teach the principles of sound investing: Buy a stock only when you can purchase it at a large discount from what any rational cash-paying buyer would pay per share to own the whole business.
NEXT: Leave your money alone