One who employs this methodology is referred to as a scalper.
 Trade Frequency
Scalpers tend to make several, perhaps hundreds of trades a day, accruing a number of small profits into a respectable daily total. Losses per trade tend to be minimal, from scratch to a few ticks at most. A scalp trade would certainly never be held overnight.
Scalping is sometimes referred to as 'the quick and the dead', as it takes a lot of mental discipline, intense focus and quick reactions to be able to scalp successfully and most people would agree that it is not for the novice trader.
 Scalping Strategies
Some scalpers work around the bid/offer, buying on the bid and selling on the offer to pocket the spread, or perhaps a tick or two more. This is perhaps the "purest" form.
Slightly longer term scalp trades (there's an oxymoron!) are generally taken from three different trading patterns:
What sets a scalper apart from other traders is that the profit target is likely to be small. While a longer term breakout trader might wait for the breakout to turn into a trend, the scalper will generally be happy to pocket a few points during the frenetic trading activity as the breakout occurs. (S)he may well trade in large size with an eye on the order flow in order to spot the optimum time to enter and exit.
Some traders will scale out most of their position for a scalp but leave some on, in order to capitalise on further price movement, should it appear. Different market conditions often require different approaches so scalping can be a tool in the trader's box as opposed to the method always used.
In most cases, and certainly for the shortest term of scalps, traders will require some knowledge of the order book, coupled with time and sales and possibly also Level II. Some scalpers work principally off the order book, reading the tape rather than making purely chart-based entries and exits.
 See also
 T2W links