Howard,
Always one in the chamber and a full magazine. If you need it, it will be under stress. I bet pulling a trigger will be the only thing on your mind, not racking in a round.
As for the magazine, these are not old Colt M16's that needed two less rounds to function and were meant to be disposable.
Load it fully, carry it often, and I hope you never need it! Practice with it from the holster you will carry it in.
Robar233