If it's not in my hands (which it is 99% of the time) I carry whatever camera I have slung across my neck so that it rests on the right side of my hip. This pertains to my Leica, my Nikons, my Rollei, and my Hasselblad.

I only take a bag if I'm carrying more than one body, or plan on picking up other things. My camera bag carries things that aren't cameras more often than cameras (water bottle, granola bars, matches, extra film, phone charger, etc.)