Swing trading refers to the practice of trying to profit from market swings of a minimum of one day and as long as several weeks. In contrast to swing traders, day traders usually are in and out of the market in one day and trend traders often hold positions for several months. So, in terms of length of holding a trade, swing traders are in between day traders and trend traders.
Commissions for direct-access brokers are calculated based on volume. The more shares traded, the cheaper the commission. The average commission per trade is roughly $5 per round trip (getting in and out of a position). While a retail broker might charge $7 or more per trade regardless of the trade size, a typical direct-access broker may charge anywhere from $0.01 to $0.0002 per share traded (from $10 down to $.20 per 1000 shares), or $0.25 per futures contract. A scalper can cover such costs with even a minimal gain.
A stop-loss order is designed to limit losses on a position in a security. For long positions, a stop loss can be placed below a recent low, or for short positions, above a recent high. It can also be based on volatility. For example, if a stock price is moving about $0.05 a minute, then you may place a stop loss $0.15 away from your entry to give the price some space to fluctuate before it moves in your anticipated direction.
There is no special qualification required to become a day trader. Instead day traders are classified based on the frequency of their trading. FINRA and NYSE classify day traders based on whether he or she trades four or more times during a five-day span, provided the number of day trades is more than 6% of the customer's total trading activity during that period or the brokerage/investment firm where he or she has opened an account considers him a day trader. Day traders are subject to capital and margin maintenance requirements.
Price action trading relies on technical analysis but does not rely on conventional indicators. These traders rely on a combination of price movement, chart patterns, volume, and other raw market data to gauge whether or not they should take a trade. This is seen as a "simplistic" and "minimalist" approach to trading but is not by any means easier than any other trading methodology. It requires a solid background in understanding how markets work and the core principles within a market, but the good thing about this type of methodology is it will work in virtually any market that exists (stocks, foreign exchange, futures, gold, oil, etc.).

The common use of buying on margin (using borrowed funds) amplifies gains and losses, such that substantial losses or gains can occur in a very short period of time. In addition, brokers usually allow bigger margin for day traders. In the United States for example, while the initial margin required to hold a stock position overnight are 50% of the stock's value due to Regulation T, many brokers allow pattern day trader accounts to use levels as low as 25% for intraday purchases. This means a day trader with the legal minimum $25,000 in his account can buy $100,000 (4x leverage) worth of stock during the day, as long as half of those positions are exited before the market close. Because of the high risk of margin use, and of other day trading practices, a day trader will often have to exit a losing position very quickly, in order to prevent a greater, unacceptable loss, or even a disastrous loss, much larger than her original investment, or even larger than her total assets.

Trending stocks rarely move in a straight line, but instead in a step-like pattern. For example, a stock might go up for several days, followed by a few steps back during the next few days before heading north again. If several of these zig-zag patterns are strung together, and the chart appears to be moving higher with some degree of predictability, the stock is said to be in an uptrend.

Retail investors are prone to psychological biases that make day trading difficult. They tend to sell winners too early and hold losers too long, what some call “picking the flowers and watering the weeds.” That’s easy to do when you get a shot of adrenaline for closing out a profitable trade. Investors engage in myopic loss aversion, which renders them too afraid to buy when a stock declines because they fear it might fall further.
A trader can measure their performance as a percentage of the trading channel width. The perfect trade would be buying at the bottom channel line and selling at the top channel line, which would be a 100% performance. If a trader captured one-half of the channel, it would be a 50% performance. The goal is to continually increase the performance percentage of the average winning trade.
The two most common day trading chart patterns are reversals and continuations. Whilst the former indicates a trend will reverse once completed, the latter suggests the trend will continue to rise. Understanding these trading patterns, as well as ‘triangles’, ‘head and shoulders’, ‘cup and handle’, ‘wedges’ and plenty more, will all make you better informed when it comes to employing your trading strategies.
Ultimately, each swing trader devises a plan and strategy that gives them an edge over many trades. This involves looking for trade setups that tend to lead to predictable movements in the asset's price. This isn't easy, and no strategy or setup works every time. With a favorable risk/reward, winning every time isn't required. The more favorable the risk/reward of a trading strategy, the fewer times it needs to win in order to produce an overall profit over many trades.
Scalpers buy low and sell high, buy high and sell higher, or short high and cover low, or short low and cover lower. They tend to utilize Level 2 and time of sales windows to route orders to the most liquid market makers and ECNs for quick executions. The point-and-click style execution through the Level 2 window or pre-programmed hotkeys are the quickest methods for the speediest order fills. Scalping is purely based on technical analysis and short-term price fluctuations. Due to the extensive use of leverage, scalping is considered a high-risk style of trading.
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.