Traps need to be stored the same as rodenticides. Make sure that no pesticide gets near the traps. I like to see them stored inside plastic sealed containers, along with the product that you are going to use as trap bait. Although studies have shown that human odors do not repel rodents, I have always worn disposable gloves when handling snap traps. Your odors may not affect the rodents, but things that you may have touched probably will.
Gloves are also a good practice for handling dead rodents.
There are all kinds of baits that can be used to entice rodents into traps. My favorites include peanut butter, kitty malt, molasses, jujubes and cotton balls. If you are going to use peanut butter or any nut product, make sure that you check with the client to ensure that there are no nut allergies. Never get stuck on one kind of bait, either, because mice will change their eating habits frequently. I always try to use at least two baits to see what they are taking.