1) When you get wider wood, take a slightly wider stance.
2) Keep your gaze on the floor the entire time (you are shifting your gaze/head during the reps).
3) When you take your breath, bear down on your abs, don't puff your belly out.
4) You need to lean over more when you start the rep. Watch what happens as you rise out of the bottom: your body leans you over a bit more as you come up - that is the lean you want on the way down.
5) Shove your knees out a touch harder as you initiate each rep.
6) Try and not let your breath go as you ascend.