The answer to 'how to maintain shut-off valve' is to regularly inspect and operate the shut-off valve to ensure it is functioning properly. This involves turning the valve handle clockwise to the fully closed position, then counterclockwise to the fully open position to check for smooth operation and no leaks.
It's recommended to perform this maintenance check on all shut-off valves in your home at least once per year, or more frequently if the valve is used regularly. If you notice any issues like the valve sticking, leaking, or not fully closing, it's best to call a professional plumber to assess and repair the valve.