For virtually all day traders, the following factors are critical:
Volatility is the range of a security's price fluctuations. Volatility benefits day traders since it gives them more opportunities to profit from short-term price movements.
This is the number of times a security is bought and sold during a trading session. A trader uses the trading volume to determine the level of interest in a security. A higher volume, like a higher volatility, indicates more opportunities for day trading.
The bid-ask spreads in a security's price are affected by liquidity. Low bid-ask spreads are crucial for successful day trading since they help reduce transaction costs.