If you're talking about a sideline or end-corner trap then the key is to turn the man with the ball toward the sideline just before the double team. That keeps him from seeing the double coming and from splitting the two defenders once the trap takes place. It's a thing of beauty when it's done right - the only passing lanes the guy has are to either side down the sidelines since his back is toward the middle of the court. Needless to say you don't so much worry about rotating in the classic manner, you just make sure you guard the guys that are in position to bail him out.
The trap at the half court line is another thing - rarely can you prevent the guy from seeing the double team coming. Consequently, all five defensive players have to be involved before the springing of the trap, if you want to have much hope of it working. Normally, teams put the other three in a zone like pattern - the C at about the FT line and the other two guys trying to get in whatever passing lanes the trapped player has. Of course, it's pretty hard to use this trap effectively on a good, experienced PG, so it's often used in conjuntion with a full court press where you try to get the ball out of the hands of the PG before it gets to mid-court. The 8-sec clock helps, too, since a team may not have time to do anything but cross the line into the trap even though they can see it coming.
I've often wondered whether fans would like the game if the league would go to a six-second clock on getting ball over mid-court. I'm assuming that would be short enough that a good full court press would have a decent chance of forcing a time violation. That would be a heck of an incentive for teams to press much more, especially when behind near the end of the game. Of course, teams would also counter by developing strategies to get the ball across in time and, almost certainly, strategies for attacking the press. I'm pretty sure I'd like the game better but there is the possibility that it would change it too drastically. In the long run it might change the basic equation of the game so that sheer height lost a fair amount of it's value.