Store in a dry environment, with no extreme temperature variation. (Meaning don't keep a green laser in the car - though I am guilty of this.)
While many of our laser hosts are built like tanks on the outside, on the inside they are fairly delicate, and a drop can easily break a solder point from driver to diode, or driver to spring, etc,.
I just received a dead laser the other day... shipped with zero padding in a cardboard envelope... bad, BAD idea. Even the lens was rattling around in the mount... obviously it's going back to the seller.
So in general if there is one bit of advice to be given, it's to just be gentle with them.