The biggest deadlift problem? Not having a proper setup in terms of where the bar path begins and ends.
In short, don't set up where the bar is too far away from your shins. This creates a large lever arm for the lower back and huge sheering forces.
The bar should start right beneath the shoulder blades, close to the shins. This will set you up for a proper pull – the bar will go up and down in a straight line.
If a trainer were to come to us and say he had a method of ab training that would reduce the waist size of anyone in three weeks, we'd ask him what he was selling and then kick him out the door. Luckily, Don Alessi was a fast talker and before we could introduce him to the sidewalk, he'd convinced us that he had some pretty nifty ideas.