Possibly the most common mistake I see when deadlifts get heavy is the bar drifting away from the body.
Many lifters assume that a deadlift is just picking the bar straight up, but this isn't effective. As you pile on the plates, you need to think about actively engaging the lats and pulling the bar back into your body so that your weight shifts backward slightly.
Keeping the bar in tight helps ensure every pull is smooth and efficient.
Keep your lower back flat. Completely exhale as you lower your legs and arms to the floor. Inhale on the way back up. Keep the non-moving limbs still. Add a band to ramp it up.