No Man’s Land

"No man's land" is that area on the slide between positions. For example, if you're playing first position Bb and slurring to fourth position G, the area between those two positions would be considered "no man's land". I would advocate trying your best to not spend too much time in this area. Always move the slide deliberately and with a purpose. I am NOT an advocate of moving the slide as quickly as possible, but I am an advocate of being very deliberate and confident with your slide motion. Many players spend a lot of time fishing around between positions or moving in a very tentative fashion from one spot to the next. Either be in a position or deliberately moving to the next position. Being hesitant is almost never a good thing. 

A good way to tell if you're doing this properly is to video record yourself playing. Watch the video with no volume and see if you can tell what rhythm you are playing. I find that the people with the best slide technique often have a slide motion that is clear enough that a rhythmic dictation could be taken from it. Try your best to move the slide in a smooth, deliberate fashion that reflects the rhythm you are playing. In an effort to do this, please resist the temptation to jerk the slide in a muscular, uneven fashion. The goal is to find a nice balance between clarity and fluidity. It takes a lot of practice but makes a huge impact on the precision of your playing when you get it right.