The most common mistake I see among intermediate squaters and deadlifters is over utilization of the lower back under utilization of the glutes. Anytime you are bent at your hips, you are supposed to straighten out by squeezing your glutes to thrust forward until you are standing up straight. I think the reason why this is the most common mistake is that 'squeezing the glutes' isn't mentioned in the most popular squat and deadlift t-nation articles. This is where a lot of beginners go to learn about deadlift and squat technique:
http://www.t-nation.com/readTopic.do?id=459775
http://www.t-nation.com/readTopic.do?id=459744
The articles do mention glute and hamstring utilization, but do not specifically mention squeezing the glutes. Some may do this automatically when their form looks perfect. For others such as myself, the form may look perfect but the glute involvement is not there.
How can you tell if you are using your lower back too much?
If your lower back is sore the next day, you're doing it. I learned about this in this thread:
http://www.sosuave.net/forum/showthread.php?t=128578
"Focus on bringing the hips forward. If you get sore, it will be in the glutes/hamstrings/upperback/traps. The only thing the lower back does is staying rigid against the load. There's no movement from the lower back during the whole lift"
"Your knees extends. Your hips extends. What does your lower back do? Nothing. Just staying rigid during the whole lift. The weight on the bar tries to bend your back. But you're not (if you're deadlifting the way you should at least). This is what builds a strong lower back: the weight trying to bend your lower back, but you holding your back straight against the load."
Edit: The guy who wrote those quotes is a very experienced lifter. He's been lifting for 10 years and is currently making a living off of giving advice about health/nutrition/strength training. He also wrote the articles I cited below. Check out his site for yourself to judge his wisdom and knowledge.
Squeeze your glutes as if you if your trying to crush a rock with your butt. Thrust your hips forward powerfully. Thats how your go up for the deadlift and squat.
More info on what I'm talking about
:
http://stronglifts.com/7-tips-for-a-safer-deadlift/
http://stronglifts.com/5-reasons-you...ing-deadlifts/
http://stronglifts.com/21-tips-to-im...-avoid-injury/