Day trading for beginners is like taming a lion, except more expensive. It’s a risky and challenging pursuit: buying stocks and selling them again in the same day, making money off tiny fluctuations in the price of a stock over a six-hour period. For many years the tools of day trading were not available to the average investor. Today with high-speed Internet connections and a lot of nerve, anybody can day trade. If you have a stout heart, here’s what you can do to avoid common and costly mistakes.