In parallel to stock trading, starting at the end of the 1990s, several new market maker firms provided foreign exchange and derivative day trading through electronic trading platforms. These allowed day traders to have instant access to decentralised markets such as forex and global markets through derivatives such as contracts for difference. Most of these firms were based in the UK and later in less restrictive jurisdictions, this was in part due to the regulations in the US prohibiting this type of over-the-counter trading. These firms typically provide trading on margin allowing day traders to take large position with relatively small capital, but with the associated increase in risk. The retail foreign exchange trading became popular to day trade due to its liquidity and the 24-hour nature of the market.
Commissions for direct-access brokers are calculated based on volume. The more shares traded, the cheaper the commission. The average commission per trade is roughly $5 per round trip (getting in and out of a position). While a retail broker might charge $7 or more per trade regardless of the trade size, a typical direct-access broker may charge anywhere from $0.01 to $0.0002 per share traded (from $10 down to $.20 per 1000 shares), or $0.25 per futures contract. A scalper can cover such costs with even a minimal gain.

Scalpers need to be disciplined and need to stick to their trading regimen very closely. Any decision that needs to be made should be done so with certainty. But scalpers should also be very flexible, because market conditions are very fluid and if a trade isn't going as expected, they'll need to fix the situation as quickly as possible without incurring too much of a loss. 
Liquidity - The liquidity of a market affects the performance of scalping. Each product within the market receives different spread, due to popularity differentials. The more liquid the markets and the products are, the tighter the spreads are. Some scalpers like to trade in a more liquid market since they can move in and out of large positions easily without adverse market impact. Other scalpers like to trade in less liquid markets, which typically have significantly larger bid-ask spreads. Whereas a scalper in a highly liquid market (for example, a market maintaining a one-penny spread) may take 10,000 shares to make a 3 cent gain ($300), a scalper in an illiquid market (for example, a market with a 25 cent spread) may take 500 shares for a 60 cent gain ($300). While there is theoretically more profit potential in a liquid market, it is also a "poker game" with many more professional players which can make it more difficult to anticipate future price action.
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).
Swing traders should select their candidates from the most actively traded stocks and ETFs that show a tendency to swing within broad well-defined channels. Virtually all trading platforms provide a function to enter channel lines on a price chart. The trader should keep a list of stocks and ETFs to monitor on a daily basis and become familiar with the price action of their selected candidates.
Because scalpers focus on short-term positions with low-profit margins, the best scalping strategies (such as the Triple S strategy mentioned below) require some leverage. It's recommended that scalpers start with a large amount of capital. Opening and closing larger positions allow you to reduce the marginal costs of trading and maximize potential gains.
Individuals who attempt to day trade without an understanding of market fundamentals often lose money. Technical analysis and chart reading is a good skill for a day trader to have, but without a more in-depth understanding of the market you're in and the assets that exist in that market, charts may be deceiving. Do your due diligence and understand the particular ins and outs of the products you trade.
Although they’re usually not as orderly as an uptrend, downtrends also tend to move in a step-like or zig-zag fashion. For example, a stock could decline over the course of many days. Then it may retrace part of the loss over the next few days before turning south once more. When this behavior is repeated over time, the downtrend of the chart becomes easier to see. The move downward is the trend itself, with bear rallies or retracements being visible as the counter trend.
Many orders placed by investors and traders begin to execute as soon as the markets open in the morning, which contributes to price volatility. A seasoned player may be able to recognize patterns and pick appropriately to make profits. But for newbies, it may be better just to read the market without making any moves for the first 15 to 20 minutes. The middle hours are usually less volatile, and then movement begins to pick up again toward the closing bell. Though the rush hours offer opportunities, it’s safer for beginners to avoid them at first.