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.
Traders following the Breakout Intraday Trading Strategy identify a price level which can be their breakout trading level, wait for a breakout and identify the resistance level and then wait for the break out to close above the resistance level. However, breakout trading is quite risky as the traders are buying the security that everyone else is, and there is hardly anyone left to buy it after the traders get in.
Sincere interviewed professional day trader John Kurisko, Sincere states, Kurisko believes that some of the reversals can be blamed on traders using high-speed computers with black-box algorithms scalping for pennies. “That’s one of the reasons many traders get frustrated with the market. The timing is not like it used to be, and many of the old rules don’t work like before.” [2]

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. 
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