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.
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). 
On the other hand, a bearish crossover occurs when the price of a security falls below these EMAs. This signals a potential reversal of a trend, and it can be used to time an exit of a long position. When the nine-period EMA crosses below the 13-period EMA, it signals a short entry or an exit of a long position. However, the 13-period EMA has to below the 50-period EMA or cross below it.

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]
The intraday trading strategy to be used also depends upon the traders’ personal trading styles, along with being dependent on the market conditions. Some traders are very active and do many trades a day, with large position sizes, catching even the small price movements; while there are others who trade only on specific news events or only on tendencies that they have well researched.
In addition to knowledge of basic trading procedures, day traders need to keep up on the latest stock market news and events that affect stocks—the Fed's interest rate plans, the economic outlook, etc. So do your homework. Make a wish list of stocks you'd like to trade and keep yourself informed about the selected companies and general markets. Scan business news and visit reliable financial websites.