What is the "ultimate" calibration method?

Take at least 25 bias, dark, and flat-field exposures. Use the same temperature as the light frame for all, and use the same exposure for the dark frame as the light frames. Turn on the Auto Scale feature, and use the "Apply to Flats" option for dark frame scaling. Use median combine if you have any hot pixels or cosmic ray hits. If you are doing median combine, it's a good idea to increase the number of calibration frames somewhat.