Proper tracking reduces the load on belt guides and ensures that the front and rear rollers are parallel. Follow the manufacturer's directions on belt tracking to keep from misaligning or over-stretching the belt. Be careful not to over-tighten belt when adjusting alignment. Use a level to level treadmill with floor. Squeaking sounds and belt mistracking are most often the result of a non-level floor.
Treadmills usually have level adjustment in rear supports.
If your treadmill cannot be leveled with the floor, then level the floor with your treadmill. Keep power cord free and clear from treadmill. Make especially sure the power cord is clear of the incline mechanism. Keep belt and deck dry. Unless recommended by the manufacturer, avoid use of silicone or oils to lubricate the belt.