Assess how much capital you're willing to risk on each trade. Many successful day traders risk less than 1% to 2% of their account per trade. If you have a $40,000 trading account and are willing to risk 0.5% of your capital on each trade, your maximum loss per trade is $200 (0.005 x $40,000). Set aside a surplus amount of funds you can trade with and you're prepared to lose. Remember, it may or may not happen.

The key to scalping while using short time frames is to identify price changes before the rest of the market has had the chance to act. You should also be willing to accept very low profit margins—gaining less than 1% on a given action will still usually be in your best interest. Because of this, many scalpers may implement tight stop-loss and stop-limit orders over time.  
Individual traders often manage other people's money or simply trade with their own. Few of them have access to a trading desk, but they often have strong ties to a brokerage (due to the large amounts they spend on commissions) and access to other resources. However, the limited scope of these resources prevents them from competing directly with institutional day traders. Instead, they are forced to take more risks. Individual traders typically day trade using technical analysis and swing trades—combined with some leverage—to generate adequate profits on such small price movements in highly liquid stocks.
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.