How do you pick a designated driver? Simple, it's the one who is too drunk to sing.
Waaaaaay back in high school, a group of us would hop in a car and head off for a night at the bars. On more then one occasion, a state trooper would pull us over and after shining the flashlight in each of our eyes, he would ask if any one of us in the car had less than two beers tonight. As if on cue, everyone would turn and point to Jeff who was, of course, sitting scrunched up in the backseat of the car, furthest from the steering wheel. The trooper would then "recommend" that Jeff should switch seats with the driver. After a two or three block escort, the trooper would turn off in another direction and we'd be on our merry way.
My how things have changed. Now you can't even drink in a bar of all places!