Disassemble your trumpet by removing the mouthpiece, tuning slides and valve slides. These items should be removed before the valves are taken from the trumpet.
Unscrew the first valve nut and gently pull the valve upward. When the valve is halfway removed, inspect the valve for the number "1." It is stamped on the inside of the valve. Take note of the direction the number is facing as you will replace the valve in the exact same position and direction. Pull the valve the rest of the way out.
Remove the second and third valve, again taking note of the direction the stamped number faces. Remove the valve caps.
Place all three valves in a cup of warm, soapy water with the valves submerged. Do not let the felt touch the water.
Scrub the valves and the empty space where the valves were housed with a valve casing brush. Clean them with an upward and downward motion. Place the valves on a towel or cloth and allow them to dry.
Screw the valve caps back into the trumpet. Oil the valve labeled "3" and place it back in its original position, ensuring that the number is aligned as before. Once the valve is in place, twist until you hear a click and use the valve nut to screw it into place. Follow these same steps for the remaining two valves, ensuring that the valves are placed tightly.