Light singles: I teach the student to establish the takeoff attitude when the elevator becomes effective and let the aircraft lift off when it is ready
Light twins: I teach that the aircraft maintains a level attitude with the nose wheel on the runway until rotate speed. This is so that in the event of an engine failure on the takeoff roll the pilot will have the benefit of nosewheel steering to help maintain directional control. The only exception is the Twin Comanche. Because of its very nose high attitude on the ground care must be taken not to hold it on the ground therefore I let it lift off from the ground attitude when it is ready, so no real rotation, and then briefly hold it level in ground effect to let the speed build to a safer value and then climb away