What is proper way to use anti-lock brakes in an emergency situation?

Step on brake until the brake peddle starts to shake and make sure that it continues to until the car comes to a complete stop. (the vibration is a warning that the anti-lock system is working and there is no more braking effect available)

This ensures you are getting as much from the brakes as is possible.

If you need to steer the car while braking this way move the steering GENTLY!!