Even a grey card and a hand held meter aren't always usefull. When I'm shooting stuff for work I always bracket exposures, always. Ofcourse the experience you have with your film and your camera (considering that it always produces stable results, or at least the same errors in the same situations) you'd use that as your starting point. For normal situations I always shoot in Aperture-priority mode, cause the shutter speeds are of no interest to me, I use spot metering, pick my grey tones from the scene and not from a card, simply because light is never consistent outside (and in large areas) and I lock the exposure and start bracketing. But when I'm shooting for fun I just shoot once, with Velvia usually keeping it at -0.3 EV, unless the situation requires me to do otherwise. But slight underexposure gives me far better results on Velvia, instead of using matrix metering and let the camera figure it all out. And for low light situations there is no reason not to use bracketing (read tutorial ;) Take care....great question btw!