The first thing that you should do is drain the water out of it right after you take it out for the last time, at this time the jet ski should be tilted back. Run the engine several times for no longer than 30 seconds each time. Tilt the handle back and forth while the eingine is running to drain the water. Use mild soap and water to scrub the outside of the jet ski. Wash it everywhere to get all the algae and everything else off. Make sure there is no water in the hull of the jet ski. You can use a normal wax to give it a protective shine. Fill the tank before you put it away for winter. Add stabilizer according to the directions on the bottle and make sure you keep the gas clean for the next season. Run the engine in 30 second intervals several times to get the stabilizer mixed before storing. Remove the air filter to allow easy access to the carburetor. Spray fogging oil in the carburetor’s and spark plug cylinders. Spray the oil while the engine is idling. Continue spraying until the engine stalls and then replace the air filter.Take out the spark plugs. Make sure the wires are grounded first. Spray fogging oil into each spark plug hole. Put a rag over each hole and push the start button to disperse the oil. The won’t start because the spark plugs are not in place. Replace the plugs and clean up any mess left. Remove the battery, negative connection and then the positive connection. Store the battery in a warm clean area. The trailor tires will rot if they are left on gravel or dirt.Cover them with plastic bags and put boards under them.to keep them from rotting remove them from the trailor and put the trailor on blocks.Store the jet ski on the trailor with the tires off for best wheel maintenance.Place steel wool in the tail pipe so the animals won’t get in it. Cover the jet ski for the winter.