In the perfect pulling position, your chest and head are up, back arched, arms straight down from your shoulders and locked, knees flared, and weight balanced over the middle of the foot or shifted slightly towards your heel. Now remember, the deadlift is a TOTAL BODY LIFT!!! I think of an explosion from the middle of my body…my feet are driving through the floor, my upper back is tight and pulling back, and I'm trying to force my chest and hips through to the top. Synchronicity is key here; since you don't have a stretch reflex like the squat, your have to have everything firing at once to move the heavy tonnage.
Some people state that you should only perform singles when doing deadlifts. I agree to an extent, but I think there are times when doing no-pause deadlift reps are good as well. Beginners, especially those just learning the powerlifts, can benefit from doing continuous reps without a pause for several reasons: 1) It teaches them the most efficient position to pull from, especially since you can't always get that feel on the first one, 2) It allows you to go slightly heavier than you normally would, and therefore overload the muscles necessary for deadlifting (assuming you can get the first one up!) However, for most advanced trainers who have no prominent muscle imbalances or technique issues, I would stick to sets with pauses in-between reps or singles to further increase performance.