Full-fielding the alternator means the alternator will put out the maximum voltage/amperage it is capable of producing. Somewhere around 18-20 volts and it's amperage rating. Not good for electrical systems, or the alternator.
BTW, it is poorly shown in my crude diagram above, but the center pin of the volatge regulator is ignition switched 12 volts. The upper right pin (as you look at the front) is the regulated ground. Upper left is not used.
The voltage regulator grounds itself through its case, so make sure it's mounting bolts are clean and tight. To ensure a good VR ground, you can run a short ground wire from one of the mounting bolts to a good chassis or engine block ground. However this is only needed if you cannot provide the VR a good mount-point ground for some reason.
-S/6