NEVER STOP LEARNING
Perhaps the most important rule is learn, learn more, and then keep learning. The fun thing about investing is that the markets are always different and companies are constantly changing. Never stop learning about businesses, never stop learning from other great investors, and never stop learning from your own mistakes. Humility and an eagerness to learn are two traits found in all of the great investors. Even Warren Buffett credits his partner Charlie Munger with teaching him that it's better to buy a great company at a fair price than a fair company at a great price.
"The game of life is the game of everlasting learning. At least it is if you want to win." Charlie Munger