Here are a few pointers that may help:

1) Don't try and "lift" the weight, concentrate on driving your feet through the floor, so to speak.

2) Arch your back by sticking your chest out like you are a hot female porn star about to do a scene in a classro.. Disregard the second part of this.

3) Tighten your triceps and keep your arms totally straight.

4) Concentrate on keeping your midsection tight, it may help to actually flex your abdominals during the motion.

5) Arms should be perpendicular to the ground.

6) ALWAYS look up during the lift (this helps assure #2)

That's all I can think of for now. More to come hopefully.