Cabbage heads should be large and compact (not fluffy), heavy for their size, with tender green leaves showing no evidence of damage or insect nibbles. Check the bottom of the cabbage to be sure the leaves are not beginning to separate from the stem, this is an indication of age.
Remove the wilted, discolored, and thicker outer leaves. Rinse under cold running water. Cut the cabbage head lengthwise in half and then into wedges (or quarters). If there are signs of worms or insects after the head is cut open, rid the cabbage of them by soaking it in salt water for 20 minutes.
Make sure that the cabbage remains uncut (until ready for consumption) to prevent vitamin C loss. Place the uncut head in a perforated plastic bag and store up to two weeks in the refrigerator crisper drawer. If the cabbage is cut, wrap the remainder of the head tightly in plastic wrap but use within a couple of days.