OK so Im in my first year of University at the Queensland COnservatorium of Music in Australia. Throughout this first semester I have been focusing on getting a rich dark sound.

anyway my teacher showed me this excersise he does and everyone I believe should do.

Set metronome at crochet = 48
Breathe in deeply on the 4th beat right up until the 1st beat and then play on the 1st and 2nd beats, when the 3rd beat comes pull the instrument away from you mouth and continue blowing out all the air until empty in one beat. Start this exersise on the 'F' middle of the Bass cleff and work out chromatically. eg. 'F' F# E G Eb Ab D A etc.
remember to keep open and keep things free and easy. thats the key word EASY.

Have fun with playing and try and do this excersise continue it up to top Bb. or if you feel things changing only to the G