I think I have every setting covered (via the info I've gathered from JDS, Barry, Ben B, etc.) but I don't know what setting I should use for the "metering" setting.
Thinking about it... maybe some of the banding problems arise from multimetering. Say you've got a shot of someone in room at night sitting at a table illuminated by a modest desk lamp. Multimetering might encourage you to try to expose for the dark room as well as for the subject. Spot metering the brightest part of the subject and allowing for the dark room to disappear into black might avoid banding and other noise. Better perhaps to (in essence) not expose the dimly lit walls, rather than to underexpose them and reveal noise.
Thinking aloud here... perhaps I'm wrong... but it's part of considering what metering mode to use in what situation.
The metering tells the camera what settings to use for aperture, ISO, and shutter speed - if you haven't set those yourself. If you are setting those yourself it tells you whether you are over and under exposed. The metering can be set to look at the average illumination of the whole picture, or largely the centre, or exactly the centre. If you want to have a particular spot correctly exposed and never mind the rest, spot metering is good. If you want as much as possible of the picture to be exposed, use one of the other settings.
A bit of a simplification but hopefully you'll get my drift.