Bulbs
Look for big ones -- the plumper, the better!
Roots
Make sure the roots haven’t been shaved off. This is also a hint that you’re buying (more) locally, which means fresher -- Chinese imports tend to have the roots cut off.
Weight
Pick a head that feels heavy and dense for its size. A lighter head is a sign of dehydration.
Sprouts
If there is any sprouting or there are green shoots on the garlic’s head, don’t buy it. The garlic will probably be bitter.
Firmness
You want your garlic nice and firm -- soft and spongy is a no-no.
Covering
Look for the head’s papery cover to be relatively intact and whitish, not shriveled.
Cloves
Try to peel down the covering so you can glance at the cloves themselves. You’re looking for plump, whitish cloves (as opposed to shriveled, gray or yellow ones).
-- Paula Kashtan
Dec 15, 2010