Useful tips on different aspects of brass playing:

BREATHING:

1) Breathing is the most important aspect in brass playing!

2) The breath before you play must be deep/low and relaxed not high/shallow and tense.

3) The breath and release of the air should feel like one motion. ie, never hold air in or pause between breathing and blowing/playing. This creates a tense sound and could lead to diminished confidence in the basic action of attacking and starting notes.

4) Try not to over-analyse where you are breathing from. Various terminology ranges from 'breathing from the diaphragm' to 'pushing your stomach out' or 'filling the back', etc.. all this only serves to confuse matters. Just breathe naturally without raising the shoulders and relax when blowing. It is important to eliminate any unnecessary tension whilst playing.

SOUND:

1) It sounds obvious but always listen carefully to your sound, from the first note of the day until the last!

2) When playing your first notes of the day, think of the sound you want to/are making. Don't think only of technical issues such as embouchure, buzzing, tongue position. Thinking in this inward way usually results in a tense sound and less productive "warm-up" and practice day.

3) When playing listen to what is coming out of the bell and adjust instead of thinking how you physically make the sound (ie. buzzing, the workings of the embouchure). Think outwardly and project the sound rather than thinking inwardly.

STAMINA:

1) If you are having trouble getting through a passage/piece, just slow it down. I slow the piece down, if necessary to half speed. I then take a deep, relaxed breath and play through the passage/piece until I run out of breath. I then rest for 20-30 seconds before playing again until I run out of breath once more, continuing until I finish the piece after which I rest for a more substantial period of time (ie. 5/10/15mins).

2) If you perform the above process, gradually speeding it up, it will become easier and easier. Eventually, once up to speed, the fingering/breathing/pitches will be well practiced and stamina much improved!