When playing a musical instrument, talent and dedication may be the most important aspects of good performance and improvement, but improper basic technique can interfere with the playing of even the most skilled artists. For trombone players, correct posture and correct methods of holding the instrument are of paramount importance for proper breath support, slide technique, sound projection and physical health.
Assemble the trombone correctly to be able to hold it properly. When facing forward, the slide should be to the right of the bell. Also, when sliding the inner tube of the slide into the outer tube of the bell portion, twist them together with some pressure. The two pieces of your trombone should be able to stay together even before you screw on the ring that secures them. Leave a hand's width of space between the bell and the slide.
Wrap your left hand around the trombone at the place where the two pieces of the instrument join, reaching from the outside left of the horn. The instrument is primarily gripped and held between the palm and the middle, ring and pinky fingers of the left hand.
Place your finger over the lead pipe (the place where the mouthpiece is inserted) or under the top slide brace, depending on how long your finger is. Placement of the finger over the lead pipe is more standard, but players with smaller hands may have to compensate with an altered hand position.
Rest your left thumb over the top of your trombone's trigger, if it has one. If not, simply wrap the thumb around the bottom brace on the bell portion.
Hold the slide handle between your thumb and first two fingers. Do not grip the slide with your fist, as this will interfere with its movement. Be sure to grip at the bottom of the slide handle, rather than the top, since this will prevent the bulk of the trombone's weight from being borne by your right hand (keeping weight in the left hand allows the slide to move more freely for best playing technique).
Stand or sit comfortably upright and relaxed as you would for playing, making sure that your head is positioned to look straight forward with your neck (and windpipe) unbent. Once you are in this position, lift the trombone to your face and position the mouthpiece at your lips. If there are objects in your way that prevent you from playing with good posture, move them or move yourself. Never position the trombone in such a way that your body posture is awkward as this interferes with breathing and playing.
Press the mouthpiece against your lips with as little pressure as possible. Ideally, you should play with just enough pressure to create an airtight seal between lips and instrument -- in other words, very little.