Warm the instrument by playing a series of major scales and long tones. Hold each long tone out for at least four seconds before playing the next long tone.
Place the music tuner on a stand in front of you. Play a written G on the treble clef staff by leaving all of the valves open. Pull the main tuning slide, which is the largest slide, out if the pitch is high, or sharp, and push the slide in if the pitch is flat. You will be able to tell if the pitch reads sharp or flat because of the position of the tuning needle. Aim to get the needle directly in the center of the tuner.
Play the following series of notes starting on the D directly below the staff: D, E, F-sharp and end on G holding the pitch out to see if the G is in tune. Using a scale ensures that the G stays in tune even during a scale.
Tune the middle valve slide, which is the smallest slide attached directly to the middle valve. Play an F# above middle C by holding down the second valve. Adjust the slide so that the pitch is in tune. Then play the following notes: C, D, E and F-sharp. Hold the F-sharp to check the tuning. Adjust as necessary.
Hold the D just above middle C by pressing valves one and three. Tune this note to check the tuning of the third valve. Adjust the middle length slide to make it possible to play this pitch in tune. Again, play a series of notes, but this time play downward starting on G. Check the tuning on G and then proceed through F-sharp, checking the tuning again, then move down to E and finally hold the D to double check the tuning.