I love cooking with ginger. It is wonderful in sauces and dressings. I like to use it when I marinate salmon or when I am making Asian food. I use to buy it, and I would throw half of it out because it would go bad before I could use it all. You can keep it in the freezer in a quart size freezer bag. I love this because I hate wasting stuff and love saving money.
When you need to use it, just take it out of the freezer, and peel just the end that you are going to use.
Grate the ginger with a microplane, zester, or you can use the smallest holes on a cheese grater.
The ginger is kept in the produce aisle usually with the green vegetables. You do not have to buy the whole root, you can break off what you need. They charge by the weight.