After using your diaphragm correctly it is also important using the air trough an instrument. There are a few tips that a player should apply while playing.
First, posture and holding the instrument should be natural for the player and there should be nothing to obstruct the player. If it is all right than the feeling when lips touch the instrument should be very smooth and flexible.
Second, tension on the lips is important. It should not be so nervous and so relaxed, it should be in the in between. Touch your lips on mouthpiece and find your position. Than inhale deeply and exhale into the instrument. In the first trial your lips could not vibrate, but after a few trials, it will. To vibrate the lips and to be able to prolong that vibration, air should be always fluent. Apply no pressure and always with the help of air.
The other crucial thing is the tone color. The tone color should be large, big and like you are singing “O, A or Ö” letters.
The important one in brass instruments is to use your body functions totally. Especially your neck, shallot and shoulders must be very natural. Inhale first into your diaphragm and your chest. But, when exhaling, the pressure should be on your back of your body. Briefly while playing, upper parts of the body should be relaxed and comfortable. The muscles on your lower part of your body should function properly.