While scales should be played in the entirety of your range, you should begin playing and learning them in a more middle register and work your way out to the extremes. Here is a scale pattern that has served me well over the years. The best approach is a slow one, begin working on these patterns at quarter note = 50. Be sure to play this to a drone as well, allowing for your ear to lock in. Enjoy!
Trombone
Tuba
Calvin Audis 