Experts recommend buying heads or bulbs of garlic with plump cloves that are still covered with their papery skin. Garlic that is soft, spongy or shriveled should be avoided.
Moisture is an enemy. At home it is best to keep garlic dry, cool and exposed to the air. Do not refrigerate heads of garlic or store them in tightly wrapped plastic bags. In a proper environment, heads can last six months.

