Modern ski ropes have a loop weaved right into the boat-end of the rope. This loop, when attached properly to the boat's tow hook, can last for years. There are a number of manufacturers making different designed tow hooks, but the rope is usually attached the same way for each. The important thing is to keep the rope fastened to the hook while a person is being pulled by the boat and to keep the rope up out of the water so the propeller doesn't get it.
Open the loop in the boat-end of the ski rope.
Place the loop down over the ring-enshrouded tow hook.
Grip the leading edge of the open loop. This would be the end closest to the boat. Push it back through the ring and up over the tow hook.
Pull the ski rope tight to ensure that the loop in the rope fastens tight to the tow hook inside the ring. (See Resources for a picture of this.)