Choose a large firm root, juicy and aromatic, with smooth skin and a nice light brown color. It should not show any blemishes, mold or shrivelling. 

If you can find young ginger, it will be more tender and less strong.

The longer the rhizome, the more mature it is and therefore stronger and more fibrous.

Quality is based on the tenderness of the root and on its flavor.

Fresh - Will keep easily for 3 weeks in the refrigerator wrapped in paper towel. Avoid putting it in the vegetable crisper, which is too humid and will lead to mold. Instead keep it on the shelf, and if a little mold appears, just scrape it off. 
It will also stay fresh for about a week in a dry place. 

Ginger rhizomes can also be frozen, wrapped in plastic wrap. Take it out when needed, grate what you need, and return the ginger as quickly as possible to the freezer. When defrosted it becomes soft and difficult to grate.

Dry - in a airtight container away from light and heat.

Paste - sold in a tube, it must be refrigerated after opening.

Pickled - sold in a jar, it must be refrigerated after opening.

Tip
You can also peel the root and let it steep in dry sherry or white wine in the refrigerator until needed.

You can peel, slice, grate, chop or cut in fine sticks, depending on how you will use it..

When the ginger is young and fresh, just peel it. If it is mature and fibrous, it is better to grate it. However, there's no difference if you're adding a piece of ginger to a braise or stew simply to extract its flavor.

Cut the piece of the rhizome that you'll need, and peel it just before using to keep it from drying out.

If frozen, ginger should be grated before it thaws, because it tends to soften when it thaws, making it more difficult to work with. 

When ginger is dry, let it soak for two hours in warm water before using it.

Fresh grated or chopped ginger
Ginger is the cook's friend: it gives depth to sauces and lightens fatty meats like duck - its affinities are endless! It goes as well with garlic as with citrus, and is as suited to the most delicate meats as to the strongest. It is excellent in any savory dish to add an exotic note. It gives a unique flavour to mulled wine, drinks and cheeses. It enhances soups and curries. And it is also welcome for flavouring cakes, breads and desserts.

Remember that the later in the cooking time it is added, the more pronounced its flavour will be.

Consider adding it to a vinaigrette consisting of oil, vinegar, honey and soy sauce. You can also add some to tea water or to make an infusion to serve at the end of a meal: heat 1/2 tsp. grated ginger and 3-4 cardamom seeds in a cup of water, or half water, half milk. Strain. Serve hot or iced.

Candied or crystallized ginger
It is used in cookie, cake or other dessert recipes, among other things. Finely chopped, it is excellent in whipped cream. 

Dried ground ginger
It is used in bread and pastry making and candy making. It's also a perfect spice to enliven pumpkin soup, in conjunction with nutmeg. Finally, ginger is an ingredient in the quatre-épices blend used in many French recipes. 

It is easy to make your own powdered ginger. The version sold in supermarkets has often lost all its taste. When you make it yourself, it will keep its flavor for several weeks: the same as fresh ginger with a sweet note and nice yellow color. See the recipe. 

Ginger Sauce
Grated ginger, minced onion, parsley, one part soy sauce to two parts water, a dash of rice vinegar and the juice of half a lemon. 

The Chinese flavor poultry and season seafood with ginger. In Asian countries it is often used in combination with soy sauce. The English adore it in jams and chutneys.

The combination of garlic and ginger is inextricably linked to Creole cooking. A simple roast pork rubbed with this mixture will take on a sublime tropical flavour.

In Japan, it is soaked in brine to give it a purply-pink colour. It is then sliced thinly on a mandolin to be the essential partner of sushi. 

Refreshing and invigorating, ginger juice is very popular in Africa where it is held to have therapeutic and aphrodisiac properties. See the Senegalese recipe.