6 personal fouls = ejection. The ref raises a clenched fist. Shooting fouls give free throws. Non-shooting fouls give the ball back (unless in the bonus). The "bonus" starts after the 4th team foul per quarter.
Taking more than 2 steps without dribbling. The ref rolls their fists. The "gather step" makes it confusing — players get an extra step while gathering the ball. LeBron's crab dribble. Harden's step-back. The rules are... flexible.
24 seconds to shoot. The ball must hit the rim. If it doesn't, turnover. The shot clock resets to 14 seconds on offensive rebounds (changed from 24 in 2018 to speed up the game).
Each coach gets 1 challenge per game. Must use a timeout to challenge. Can challenge: personal fouls, out-of-bounds calls, and goaltending. If successful, you keep your timeout. If wrong, you lose it. Most coaches save it for the 4th quarter.
Flagrant 1: Unnecessary contact. Free throws + possession. Flagrant 2: Unnecessary and excessive. Ejection. Two Flagrant 1s in a game = ejection. The line between "hard foul" and "flagrant" is whatever the ref feels that day.