I've said it before and almost proved it again - it's easy to forget about your garlic plants. Most of us put them in the ground in late fall, just before the ground disappears for the winter. Since garlic requires so little care, you may not notice it again until the leaves start to turn brown, telling you it's ready to harvest.
So your garlic bulbs are signaling that they are done growing. Now what? Fortunately garlic is as easy to harvest as it is to grow. Probably the hardest part of digging up your garlic is making sure you don't slice through it. Even if you do, you can still clean it up and eat it. It won't store well sliced, but you have to sample your hard work anyway, right?
I've always considered this a good time to remember to order my garlic for next fall, too. Of course, you can save some cloves from your harvest to re-plant. But if you want to try something new, get your order in soon, so that it's delivered in time to plant. My favorite place to order garlic is Seed Savers Exchange. They have a great selection.