Shut off the water to your sprinkler system using the valve in your yard. The sprinkler valve box in your yard should be next to the valve you turn to start the sprinkler system.
Remove the top cover of the valve box. Depending on the type of valve box, the cover may be secured with latches or screws. If it is secured with screws, use a Phillips screwdriver to remove the screws on the cover.
Use your hands to remove all gunk and stones from the inside the box. You may want to wear gloves. Wipe down any excess debris with a towel or rag.
Replace the top cover of the valve box.