The common use of buying on margin (using borrowed funds) amplifies gains and losses, such that substantial losses or gains can occur in a very short period of time. In addition, brokers usually allow bigger margin for day traders. In the United States for example, while the initial margin required to hold a stock position overnight are 50% of the stock's value due to Regulation T, many brokers allow pattern day trader accounts to use levels as low as 25% for intraday purchases. This means a day trader with the legal minimum $25,000 in his account can buy $100,000 (4x leverage) worth of stock during the day, as long as half of those positions are exited before the market close. Because of the high risk of margin use, and of other day trading practices, a day trader will often have to exit a losing position very quickly, in order to prevent a greater, unacceptable loss, or even a disastrous loss, much larger than her original investment, or even larger than her total assets.
Order execution: A novice needs to master the art of efficient order execution. A delayed or bad order can wipe out what little profit was earned and even result in a loss. Since the profit margin per trade is limited, the order execution has to be accurate. As mentioned above, this requires supporting systems such as Direct Access Trading and Level 2 quotations.
Scalpers use technical analysis but within this style, can be either discretionary or system traders. Discretionary scalpers will make each trading decision in real time (albeit very quickly), whereas system scalpers follow a scalping system without making any individual trading decisions. Scalpers primarily use the market's prices to make their trading decisions, but some scalpers also use one or more technical indicators, such as moving averages, channel bands, and other chart patterns.
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.