There is a lot of hype around day trading. Some websites promote it as a way to get rich quick (it isn't), and others say it is impossible (also not true). There are lots of day traders around the world who find success and make a living off the markets, so the truth lies somewhere in between those two extremes. If you've thought about day trading, it's worth your time to read through and understand the concepts discussed below, so you'll be better prepared for what to expect if you decide to proceed.
Risk management - Rather than looking for one big trade, the way a trend trader might, the scalper looks for hundreds of small profits throughout the day. In this process the scalper might also take hundreds of small losses during the same time period. For this reason a scalper must have very strict risk management never allowing a loss to accumulate.
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.” 
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.
These developments heralded the appearance of "market makers": the NASDAQ equivalent of a NYSE specialist. A market maker has an inventory of stocks to buy and sell, and simultaneously offers to buy and sell the same stock. Obviously, it will offer to sell stock at a higher price than the price at which it offers to buy. This difference is known as the "spread". The market maker is indifferent as to whether the stock goes up or down, it simply tries to constantly buy for less than it sells. A persistent trend in one direction will result in a loss for the market maker, but the strategy is overall positive (otherwise they would exit the business). Today there are about 500 firms who participate as market makers on ECNs, each generally making a market in four to forty different stocks. Without any legal obligations, market makers were free to offer smaller spreads on electronic communication networks than on the NASDAQ. A small investor might have to pay a $0.25 spread (e.g. he might have to pay $10.50 to buy a share of stock but could only get $10.25 for selling it), while an institution would only pay a $0.05 spread (buying at $10.40 and selling at $10.35).