Act quickly and consistently. Anytime you see your child beginning to lose control, have him take a time out. Don't wait until he actually misbehaves. Choose a quiet time-out spot. Your child doesn't have to sit in a room alone.
Many children can calm down in seconds.
Long time-outs can make children disruptive. End time-out as soon as your child is ready. It's especially important to praise your child when he stays in control.