The systems by which stocks are traded have also evolved, the second half of the twentieth century having seen the advent of electronic communication networks (ECNs). These are essentially large proprietary computer networks on which brokers can list a certain amount of securities to sell at a certain price (the asking price or "ask") or offer to buy a certain amount of securities at a certain price (the "bid").
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.
Define and write down the conditions under which you'll enter a position. "Buy during uptrend" isn't specific enough. Something like this is much more specific and also testable: "Buy when price breaks above the upper trendline of a triangle pattern, where the triangle was preceded by an uptrend (at least one higher swing high and higher swing low before the triangle formed) on the two-minute chart in the first two hours of the trading day."
The second type of scalping is done by purchasing a large number of shares that are sold for a gain on a very small price movement. A trader of this style will enter into positions for several thousand shares and wait for a small move, which is usually measured in cents. Such an approach requires highly liquid stock to allow for entering and exiting 3,000 to 10,000 shares easily.

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.
Many professional money managers and financial advisors shy away from day trading arguing that, in most cases, the reward does not justify the risk. Conversely, those who do day trade insist there is profit to be made. Day trading profitably is possible, but the success rate is inherently lower because of the complexity and necessary risk of day trading in conjunction with the related scams. Moreover, economists and financial practitioners alike argue that over long time periods, active trading strategies tend to underperform a more basic passive index strategy, especially after fees and taxes are taken into account.
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). 

ECN/Level 2 quotes: ECNs, or electronic communication networks, are computer-based systems that display the best available bid and ask quotes from multiple market participants and then automatically match and execute orders. Level 2 is a subscription-based service that provides real-time access to the Nasdaq order book composed of price quotes from market makers registering every Nasdaq-listed and OTC Bulletin Board security. Together, they can give you a sense of orders being executed in real time.