From what I am always learning, one of the secrets to a good sound is proper airflow. When you play in the upper register, especially in the D2/E2+ range, the pitch tends to go very sharp because of the natural tendency to tense up. The upper register should flow just as easily as anywhere else on the horn. It takes time, patience, and discipline, but if you work on relaxing the throat and playing with an "open" feel, your sound will have more presence.
Also, by taking in a lot of mouthpiece, it makes the above easier, while at the same time, opening up the altissimo register.
Also, by taking in a lot of mouthpiece, it makes the above easier, while at the same time, opening up the altissimo register.