Spot foreign exchange (exchanges of foreign currencies) brokers - They do not charge any commissions because they make profits from the bid/ask spread quotes. On July 10, 2006, the exchange rate between Euro and United States dollar is 1.2733 at 15:45. The internal (inter-bank dealers) bid/ask price is 1.2732-5/1.2733-5. However the foreign exchange brokers or middlemen will not offer the same competitive prices to their clients. Instead they provide their own version of bid and ask quotes, say 1.2731/1.2734, of which their commissions are already "hidden" in it. More competitive brokers do not charge more than 2 pips spread on a currency where the interbank market has a 1 pip spread, and some offer better than this by quoting prices in fractional pips.
This trading strategy used to be defined as spread trading where you would take profits where small gaps expanded and contracted between the bid and the ask price for a stock. This strategy has now evolved to include technical indicators, support/resistance levels, and volume spikes to make round-trip trades lasting seconds to a few minutes. The basic idea of scalping is to take advantage of market inefficiencies using speed and high trading volume to create quick profits. Click here for more information on scalping.
The bid–ask spread is two sides of the same coin. The spread can be viewed as trading bonuses or costs according to different parties and different strategies. On one hand, traders who do NOT wish to queue their order, instead paying the market price, pay the spreads (costs). On the other hand, traders who wish to queue and wait for execution receive the spreads (bonuses). Some day trading strategies attempt to capture the spread as additional, or even the only, profits for successful trades.[18]
When it comes time to take profits, the swing trader will want to exit the trade as close as possible to the upper or lower channel line without being overly precise, which may cause the risk of missing the best opportunity. In a strong market when a stock is exhibiting a strong directional trend, traders can wait for the channel line to be reached before taking their profit, but in a weaker market, they may take their profits before the line is hit (in the event that the direction changes and the line does not get hit on that particular swing). 
Day trading requires more money than just a deposit, though. Get setup with a good computer, one or two monitors, a trading platform and data feeds. With many brokers the data feeds for various markets cost money, so pick a market and stick with it. There is no reason to pay for data feeds you won't be using. Also, a consistent income isn't likely during the first six months to a year, so save up for living expenses if attempting to day trade as a primary income stream.
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.
Due to the increased leverage and quick returns, day trading can be extremely profitable. The downside is that if done incorrectly, it can also be extremely unprofitable. Due to the high volatility of day trading, some people have labeled Day Traders as gamblers or adrenaline junkies. However, many people make a very consistent and comfortable living from day trading. Some even make millions of dollars each year.

By the same token, volume characteristics of a breakout also can have a shortened time frame. Rather than the 50-day moving average of volume as your threshold for heavy turnover, look to the volume of the shorter consolidation area for clues. If the breakout volume can surpass the recent activity, that can be a sufficient confirmation of strength.
Following the 1987 stock market crash, the SEC adopted "Order Handling Rules" which required market makers to publish their best bid and ask on the NASDAQ.[7] Another reform made was the "Small-order execution system", or "SOES", which required market makers to buy or sell, immediately, small orders (up to 1000 shares) at the market maker's listed bid or ask. The design of the system gave rise to arbitrage by a small group of traders known as the "SOES bandits", who made sizable profits buying and selling small orders to market makers by anticipating price moves before they were reflected in the published inside bid/ask prices. The SOES system ultimately led to trading facilitated by software instead of market makers via ECNs.[8]

Years ago, when stocks were quoted in fractions, there was a standard spread of 1/16 of a dollar or a "teenie". This spread allowed scalp traders to buy a stock at the bid and immediately sell at the ask. Hence the teenie presented clear entry and exit levels for scalp traders. The scalp trading game took a turn for the worst when the market converted to the decimal system. The decimal system closed the "teenie" often times to within 1 penny for high volume stocks. This overnight shifted the strategy for scalp traders. A scalp trader now had to rely more on their instincts, level II, and the time and sales window.

Spread trading This high-speed technique tries to profit on temporary changes in sentiment, exploiting the difference in the bid-ask price for a stock, also called a spread. For example, if a buyer’s bid price drops suddenly, the day trader might step in to buy and then try to quickly resell at the stock’s ask price or higher, earning a small “spread” on the transaction.

Scalping is a trading style that specializes in profiting off small price changes, generally after a trade is executed and becomes profitable. It requires a trader to have a strict exit strategy because one large loss could eliminate the many small gains the trader worked to obtain. Having the right tools such as a live feed, a direct-access broker and the stamina to place many trades is required for this strategy to be successful.

Scalping is a trading strategy geared towards profiting from minor price changes in a stock's price. Traders who implement this strategy place anywhere from 10 to a few hundred trades in a single day with the belief that small moves in stock price are easier to catch than large ones; traders who implement this strategy are known as scalpers. Many small profits can easily compound into large gains, if a strict exit strategy is used to prevent large losses.

The profit potential of day trading is perhaps one of the most debated and misunderstood topics on Wall Street. Internet day trading scams have lured amateurs by promising enormous returns in a short period. The idea that this kind of trading is a get-rich-quick scheme persists. Some people day trade without sufficient knowledge. But there are day traders who make a successful living despite—or perhaps because of—the risks.