It takes about a year to get a good ginger root and hence it is advisable to be patient. The best way to harvest the ginger plant is to wait for about 8 to 10 months and when the plant begins to die down then get the entire plant out.
If you harvest the ginger before eight months then you will have to carefully take the rhizomes out without cutting the entire plant. The ginger harvested before 8 months is typically very tender and young. This is the kind of ginger typically which is best suited for making crystallized ginger.
Once the rhizome is out, wash the dirt off then you can keep the root in a plastic bag and store in the refrigerator for about 3-4 weeks. After that the ginger will begin to lose its flavor.
Another way is to cut it into thin slices and then make it into candied ginger or crystallized ginger and that can be stored up to a year.