Day traders use only risk capital which they can afford to lose. Not only does this protect them from financial ruin, but it also helps eliminate emotion from their trading. A large amount of capital is often necessary to capitalize effectively on intraday price movements. Having access to a margin account is also key, since volatile swings can incur margin calls on short notice.
In addition to knowledge of basic trading procedures, day traders need to keep up on the latest stock market news and events that affect stocks—the Fed's interest rate plans, the economic outlook, etc. So do your homework. Make a wish list of stocks you'd like to trade and keep yourself informed about the selected companies and general markets. Scan business news and visit reliable financial websites.