How it's played
All players tee off; the team chooses the best drive; everyone plays their next shot from within a club-length of it; repeat until the ball is holed. The team records one score per hole.
Team sizes
Four-person teams are the classic; two-person scrambles move faster and put more on each player.
Handicaps
The Rules of Handicapping publish recommended allowances: for a four-person scramble, 25%, 20%, 15% and 10% of the players' course handicaps from lowest to highest, added together; for a two-person scramble, 35% of the lower and 15% of the higher. Many events add a minimum number of drives per player.
Keeping it quick
Use one scorecard per team, a shotgun start if the course allows it, and a clear rule for where the ball is placed on the green.