Know how to run a keypad without looking down at it. Be able to stand bent over for hours on end. Stand back from shelves to see all the way to the back. Lie down on the floor for bottom shelves. Know when to "batch" creatively.
It helps to be able to go for days without sleep and/or food. Be kind to your co-workers: take a shower and change your clothes if possible. Learn to chew coffee beans, keep plenty of Altoids and Advil on hand, and don't tell your family you'll be home "soon".
Remember that generic Pseudephed is cheaper than ephedrine. And get over drunk/stoned people cuz you'll be around alot of them.