A stop-loss order is designed to limit losses on a position in a security. For long positions, a stop loss can be placed below a recent low, or for short positions, above a recent high. It can also be based on volatility. For example, if a stock price is moving about $0.05 a minute, then you may place a stop loss $0.15 away from your entry to give the price some space to fluctuate before it moves in your anticipated direction.
By aggressively trading on margin he can produce 5% daily profits on the 100k buying power he will grow their 25k cash at the rate of 20% per day. The risk of course is that he will make a mistake that will cost him everything. Unfortunately, this is the fate of 9 out of 10 traders. The cause of these career ending mistakes is a failure to manage risk.
Some of these approaches require short selling stocks; the trader borrows stock from his broker and sells the borrowed stock, hoping that the price will fall and he will be able to purchase the shares at a lower price, thus keeping the difference as their profit. There are several technical problems with short sales - the broker may not have shares to lend in a specific issue, the broker can call for the return of its shares at any time, and some restrictions are imposed in America by the U.S. Securities and Exchange Commission on short-selling (see uptick rule for details). Some of these restrictions (in particular the uptick rule) don't apply to trades of stocks that are actually shares of an exchange-traded fund (ETF).
ECNs and exchanges are usually known to traders by a three- or four-letter designators, which identify the ECN or exchange on Level II stock screens. The first of these was Instinet (or "inet"), which was founded in 1969 as a way for major institutions to bypass the increasingly cumbersome and expensive NYSE, and to allow them to trade during hours when the exchanges were closed. Early ECNs such as Instinet were very unfriendly to small investors, because they tended to give large institutions better prices than were available to the public. This resulted in a fragmented and sometimes illiquid market.
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."