Once connections are secure and the slack is taken up, apply power. The rope/strap will stretch and absorb shock and jerking. If you are towing a disabled vehicle on a road, keep the rope/strap taut. Dragging the rope/strap on a road surface will fray it and eventually wear it out.
BE ABSOLUTELY CERTAIN THE HOOKS, THIMBLES, OR LOOPED ENDS ARE VERY SECURE BEFORE ATTEMPTING TO MOVE A VEHICLE. CHECK THE CONNECTIONS EACH AND EVERY TIME YOU ATTEMPT TO MOVE THE STUCK VEHICLE.
Factors such as weight, traction, and horsepower sometimes prohibit a stuck vehicle from moving. Tow ropes/straps can double or triple your pulling power, but there are limitations, and you won’t be able to move all vehicles.