To check that the ginger is indeed fresh, dig your thumbnail in it lightly. It should pierce the skin without much difficulty.
Peel the ginger root with a potato peeler. This is why you want a piece that is manageable for this, without tiny branches.
Rinse the peeled ginger. Cut up into small pieces and place in a jam jar. Pour the rice wine or dry sherry over to cover the ginger pieces. Cover and store in the refrigerator. Keeps indefinitely.
When the ginger pieces are used up, the remaining ginger-flavored wine can be used to flavor other dishes.