How does one fix a shower valve?

First decide if you want to take a shower valve repair yourself, or contact a plumber. If you decide to repair the shower valve yourself, first you will need to shut off all water to the shower and tub.Next, turn the valves to the on position to relieve any pressure, and remove the set screws. Next, remove the trim ring and save all of the gaskets. Take all of the valve parts to a home improvement store where they will assist in finding you all the replacement parts. Lastly, you'll need to put everything back together in reverse order.