Volatility is the name of the day-trading game. Day traders rely heavily on a stock’s or market’s fluctuations to earn their profits. They like stocks that bounce around a lot throughout the day, whatever the cause: a good or bad earnings report, positive or negative news, or just general market sentiment. They also like highly liquid stocks, ones that allow them to move in and out of a position without much affecting the stock’s price.
The basic strategy of news playing is to buy a stock which has just announced good news, or short sell on bad news. Such events provide enormous volatility in a stock and therefore the greatest chance for quick profits (or losses). Determining whether news is "good" or "bad" must be determined by the price action of the stock, because the market reaction may not match the tone of the news itself. This is because rumors or estimates of the event (like those issued by market and industry analysts) will already have been circulated before the official release, causing prices to move in anticipation. The price movement caused by the official news will therefore be determined by how good the news is relative to the market's expectations, not how good it is in absolute terms.
The reason is because all too often the price can drop and you will end up giving up that profit. Instead, as soon as I’ve reached my first profit target (if I’m risking $100, then as soon as I’m up $100), I’ll sell 1/2 my position and set my stop at breakeven. This method of scaling out ensures small profits on all trades that move in your favor, giving you a better percentage of success.
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. 
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.
ECNs and exchanges are usually known to traders by a three- or four-letter designators, which identify the ECN or exchange on Level II stock screens. The first of these was Instinet (or "inet"), which was founded in 1969 as a way for major institutions to bypass the increasingly cumbersome and expensive NYSE, and to allow them to trade during hours when the exchanges were closed.[6] Early ECNs such as Instinet were very unfriendly to small investors, because they tended to give large institutions better prices than were available to the public. This resulted in a fragmented and sometimes illiquid market.
Scalpers use technical analysis but within this style, can be either discretionary or system traders. Discretionary scalpers will make each trading decision in real time (albeit very quickly), whereas system scalpers follow a scalping system without making any individual trading decisions. Scalpers primarily use the market's prices to make their trading decisions, but some scalpers also use one or more technical indicators, such as moving averages, channel bands, and other chart patterns.
This is usually reserved for traders working for larger institutions or those who manage large amounts of money. The dealing desk provides these traders with instantaneous order executions, which are particularly important when sharp price movements occur. For example, when an acquisition is announced, day traders looking at merger arbitrage can place their orders before the rest of the market is able to take advantage of the price differential.
However we have a word of caution for them as intraday trading is not as simple as it sounds.Making profit in intraday trading on a daily basis is not that easy and requires lot of hard work and discipline.What are your views on this – “Whether a newbie in stock market should resort to intraday trading or not”.Drop in a comment to share your views.
Order execution: A novice needs to master the art of efficient order execution. A delayed or bad order can wipe out what little profit was earned and even result in a loss. Since the profit margin per trade is limited, the order execution has to be accurate. As mentioned above, this requires supporting systems such as Direct Access Trading and Level 2 quotations.

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.
Although day trading has become somewhat of a controversial phenomenon, it can be a viable way to earn profit. Day traders, both institutional and individual, play an important role in the marketplace by keeping the markets efficient and liquid. While popular among inexperienced traders, it should be left primarily to those with the skills and resources needed to succeed.
Finally, keep in mind that if trading on margin—which means you're borrowing your investment funds from a brokerage firm (and bear in mind that margin requirements for day trading are high)—you're far more vulnerable to sharp price movements. Margin helps to amplify the trading results not just of profits, but of losses as well if a trade goes against you. Therefore, using stop losses is crucial when day trading on margin.