This trading strategy used to be defined as spread trading where you would take profits where small gaps expanded and contracted between the bid and the ask price for a stock. This strategy has now evolved to include technical indicators, support/resistance levels, and volume spikes to make round-trip trades lasting seconds to a few minutes. The basic idea of scalping is to take advantage of market inefficiencies using speed and high trading volume to create quick profits. Click here for more information on scalping.
Futures are a contract that match up a buyer and seller at a specific price, with the buyer agreeing to pay that price for the asset when the contract expires in the future. The seller is agreeing to deliver the asset, like oil for example, to the buyer when the contract expires. Day traders are never required to deliver or pay for the actual asset, because all positions are opened and closed within the day (no open obligations). Profits are losses are based on the prices the contract is opened and closed at.
The price movements of any stock are posted throughout the trading day and summarized at the end of the trading day. For example, April 2, 2019, shares of Apple Inc. (AAPL) opened at $191.09 and closed at $194.02. During the day, as indicated in the "day's range" listed to the right of the closing price, shares dropped as low as $191.05—the intraday low—and hit a peak of $194.46—the intraday high.
The most significant benefit of day trading is that positions are not affected by the possibility of negative overnight news that has the potential to impact the price of securities materially. Such news includes vital economic and earnings reports, as well as broker upgrades and downgrades that occur either before the market opens or after the market closes.
Assess how much capital you're willing to risk on each trade. Many successful day traders risk less than 1% to 2% of their account per trade. If you have a $40,000 trading account and are willing to risk 0.5% of your capital on each trade, your maximum loss per trade is $200 (0.005 x $40,000). Set aside a surplus amount of funds you can trade with and you're prepared to lose. Remember, it may or may not happen.