Forward Slip

Check here

http://en.wikipedia.org/wiki/Forward_slip#Forward-slip

😀

my understanding is that you input full rudder and use opposite aileron to hold heading
DO NOT bank off the centerline 😂

Yes slips are an effective way to lose some altitude quickly however they should be done with caution. When you slip you are partially blocking airflow over one of your wings so if you happen to stall, that wing will stall first which will cause the plane to roll during the stall. If you do slip, keep an eye on your airspeed. Generally the procedure is to put one wing into the wind and apply opposite rudder - full rudder would give you the maximum slip.