For races, I'll warm up on a trainer. Typically, the shorter the race, the longer the warmup. For crits, the cooldown is usually a lap or two of softpedaling. For road races, it's generally an easy ride back to the car.

For just rides, I don't have a set warm-up/cool-down regimen. It's usually just taken care of by riding casually through town on the way out to or back from the open road.