Use the tools at our disposal to make practice harder. For example, Bill Belichick likes to used soaked, less than perfect footballs. Bad weather? That's how games are played in the Northeast.
Court conditions. We play 2-on-2 and 3-on-3 on one side of the split (the line bisecting the court lengthwise).
Time conditions. Run situational plays, baseline out of bounds (BOB), sidelines out of bounds (SLOB), after timeouts (ATO) with time constraints (3, 5, 10 seconds) to mimic end-of-quarter, end-of-game situations. Yesterday, we actually held for one shot effectively.
Playing conditions. Instead of starting scrimmages or half-court drills consistently from static situations, start from 'artificially real' turnovers, blocked shots, and edges. Can add constraints like no more than two dribbles per player.
Dean Smith Scoring. Scrimmage with points award according to shot quality...e.g. 2 points for layup (made or missed), 2 points for open shot, 0 points for poor shot, -2 points for turnover.
Advantage disadvantage. We always run press break either 5 on 7 or 5 on 8. We may add constraints like no dribbling. Modify 'shell'.
Confirmation (free throws). Finish a scrimmage or drill where a group wins by requiring a made free throw to 'seal' victory.
Competition. The more competitive the drills, the more they include offense, defense, and decision-making, the better.
Fatigue. "Fatigue makes cowards of us all." I really like the 3 by 3 by 3 shooting drill, which I usually run for 5-6 minutes. 6 basketballs in play. As soon as you pass, you take off and become a shooter.
Information. Stop practice during a scrimmage with a "timeout". Put in a new play (ATO, SLOB, BOB) and see whether and when players can absorb, retain, and execute the new play. We struggle with this (eighth grade girls)...but I believe it's worth it.