Cleans, snatches and all their related 'offspring' are ballistic, power movements so you have to do them fast. Or, you might decide to do paused reps for bench, squats etc. to lessen the effect of the stretch reflex. Other than that, just stick to a reasonable tempo, like Totz said.
My preference is to lift a weight quite quickly and to lower under control in ~ 2 seconds. When the loads are heavy during 5s, I move as quickly as I can while always attempting to maintain control. These reps will tend to be slower than when the loads are light.