For years coaches have been practicing situation plays. Putting time on the clock and a score on the board (20 seconds on the clock, red up 2) and saying, "Here is what we do now," has been used since Naismith. It is great for execution and it is easy to isolate the situation during a game by calling a time out.
However, I was never comfortable that I was able to teach key strategic principles between the beginning of the game and the end. There comes a time when the opponent ceases to be the other team and becomes the clock. For instance, there are shots that are fine (even encouraged) in the body of the game, but not when you are up four points with 45 seconds to go. That doesn't mean it can't be done, just that I was not comfortable with it.
We then came up with the "Time and Score" scrimmage. I am not a genius, and I am sure that I am not the first person to come up with it; however, we came up with it while trying to solve some problems, and, aside from a full game scrimmage, I now don't conduct scrimmages any other way.
How It Works
The coach decides what time frame he wants to work on (1 minute, 2 minutes, 4 minutes, 15 seconds, etc). He also decides how much regular scrimmage work he wants and translates that to points (for example, if it is mostly going to be a situation scrimmage, you might choose 4 points; if it is going to be an execution scrimmage, you might choose 10 points).
Let's say you want to run a 2-minute situation. You might choose to run a "6 and 2." Here is the way it would work: You put 2 minutes on the clock. You then run a regular scrimmage (fouls, violations, etc.). As soon as one team gets to 6 points, the clock starts. Regular time is kept. Wherever you are, that is your situation. It could be 6-5 with 2 minutes left, it could be 6-0 with 2 minutes left, or it could be anywhere in between.
Most importantly, the scrimmage does not stop when the clock starts. You just play through. You might want to announce that the clock is on, or you might choose to let the players notice on their own. Just don't stop the scrimmage to announce what the situation is. Let them learn to keep track of the clock.
During the score portion of the scrimmage, you can work on whatever you like. You work on a particular play or play package, work on your zone defense or offense, work on pressures, etc., or just play. Once the clock starts, you coach to win the game. Adjust your defense and offense to do exactly what you would do in a game. Call time outs, strategically foul, make substitutions based on roles, put on or take off pressures. You can "reset" your situation (one timeout left, both teams in the bonus, post players have four fouls, etc.). Whatever you want to do, set it up before you start the scrimmage.
You can run any combination you feel you need work on. Run a "10 and 4" for a longer scrimmage. Try a "3 and 1" for short end-of-games. I have found no better tool for teaching your players, especially your guards, how to manage a game.
This is the only effective way that I have found to teach the difference in the strategic principles for early in the game compared to the end of the game, especially for guards. There may be others that work just as well, but this has worked great for me.