none in the chamber....
Without one in the chamber is regularly called "Israeli carry" due to the Israeli Army using this procedure. Upon drawing their weapon, then are taught to grasp the slide in one motion as they present the pistol to the target. I have seen this in action and quite honestly, I am amazed they can do it with the speed and precision as fast as they do. I have had a few exhibitions with them and am ashamed to say although I was never beaten to the presentation, I rarely won. (for those of you that don't know me, this was done safely, side by side, without magazines and presenting downrange at a military base).
I personally carry a round in the chamber. You never know when your other hand may be unable to be used to rack. It may be tied up keeping an aggressor away from your gun. Just remember, if the finger is off the trigger, it doesn't go bang!!
Defensive Line CCW
Certified NRA Instructor