TIP #1: BE COMFORTABLE
Where you practice matters. If you're not in a place where you can fully focus on the single task of practicing, your session will be counter-productive; or, at best, just a waste of time.
Find a place free of distractions: from people, from extra noises, and from cell phones!
Find a chair that you're comfortable sitting in. A little cushion helps, but sometimes that's not possible. Remember, you're probably going to be practicing for a long time, so the last thing you want is a sore butt at the end of it - literally. Also important is the height of the seat, which should create a right angle from your thigh to your calf, when your foot is flat on the floor.
Find a room with good lighting. I realize that most schools use fluorescent lights - especially in classrooms. If there is any way to avoid them, do it. I used to keep a small, incandescent music stand light in my locker, and whenever I hit a practice room, I'd flip off the lights and plug in my own. It's easier on the eyes, set the mood, and allowed me to practice longer.
Finally, have a drink nearby. Set it on a chair beside you, or on a near table. Put it somewhere you can get to without stretching, reaching, or bending. (You're less likely to drink it if you have to move to get it.) Staying well-hydrated keeps your focus where it should be - on the music.
Thoughts, questions, disagreements? Post a comment.