While grabbing a dumbbell in one hand, bend forward keeping your back level with the ground. Keep your non-working hand on the bench for support. Start with the weight down by your side keeping your palm facing your body. Steadily lift the dumbbell by your side concentrating on your back doing the work rather than your bicep. Every exercise including this one should be kept under control at all times.
Spotting can be done by kneeling beside the participant and either lifting the weight itself, or standing and pulling the participants arm up.