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.
Before day trading, if someone wanted to trade a stock, they needed to call a stock broker to place their order, who would then route the order through a specialist on the floor of the exchange. The specialist would match the buyer with a seller and write up a physical ticket that would transfer the stock and send that confirmation back to both brokers. Commissions were charged at a flat rate of 1% of the total amount of the trade. That means that to buy $10,000 worth of stock, it would cost you an additional $100 in commissions. In 1975, the SEC (Securities and Exchange Commission) made fixed commission rates illegal opening up the markets to the first of the discount brokers competing for business by lowering their commissions and making short term trading much more profitable.
Different markets require different amounts of capital to day trade. Stocks are popular, but also the most capital intensive. If you want to day trade stocks in the US, the absolute minimum you need is $25,000. And you'll actually need more because you need to keep your balance above $25,000. Starting with $30,000 or more is recommended. The stock market provides up to 4:1 leverage on day trades.
The difference between the profit target and the entry point is the approximate reward of the trade. The difference between the entry point and the stop out point is the approximate risk.When determining whether it’s worthwhile to enter a swing trade, consider using two-to-one as a minimum reward-to-risk ratio. Your potential profit should be at least twice as much as your potential loss. If the ratio is higher than that, the trade is considered better; if it’s lower it’s worse.

The systems by which stocks are traded have also evolved, the second half of the twentieth century having seen the advent of electronic communication networks (ECNs). These are essentially large proprietary computer networks on which brokers can list a certain amount of securities to sell at a certain price (the asking price or "ask") or offer to buy a certain amount of securities at a certain price (the "bid").

The second type of scalping is done by purchasing a large number of shares that are sold for a gain on a very small price movement. A trader of this style will enter into positions for several thousand shares and wait for a small move, which is usually measured in cents. Such an approach requires highly liquid stock to allow for entering and exiting 3,000 to 10,000 shares easily.
Successful traders have to move fast, but they don't have to think fast. Why? Because they've developed a trading strategy in advance, along with the discipline to stick to that strategy. It is important to follow your formula closely rather than try to chase profits. Don't let your emotions get the best of you and abandon your strategy. There's a mantra among day traders: "Plan your trade and trade your plan."