I do what karky does. During the first 8 weeks of my workout, I was doing them wrong by doing it from the air and/or slighty touching the ground (getting the bar from the rack before and after each set). After I realized that it was not a deadlift, I changed my form and got help from the guy that works at the gym at school. I was able to pick up the good form right away (what he told me) and I defiantly felt the right muscles working.
A deadlift is when you lift the bar from the floor (first with your legs, and then your back) and stand all the way up, and then reverse your way back down and relax your muscles for a few seconds (between 1-5 seconds is usual depending on what weight and reps you are using), then go to the next rep.