Purse your lips together as if creating an "em" sound. From this position, separate the lips slightly.
Pull the lips tight against the teeth. The muscles around the side of the mouth should tighten. Allow the lips to drop below the top teeth and above the bottom teeth slightly.
Practice blowing air through the mouth without losing the tightness of the muscles in your mouth and without tensing the throat.
Place the mouthpiece lightly against the mouth without changing the terseness of the lips. The teeth must be separated so the lips are able to tighten to control the pitch of the note. If there is air escaping out of the side of the mouthpiece, tighten the mouthpiece slightly without hurting the teeth.
Blow air through the mouthpiece to "buzz" on it. Do not puff the cheeks, but retain muscle control around the lips.
Tighten the lips to increase the pitch. Loosen the lips to decrease the pitch.