October through December, depending on your climate, is the time of year to plant garlic. The cloves are tucked into their soil beds for the winter and are able to establish their root system early in their growth process. Their green shoots will appear in early spring, or earlier if you live somewhere with mild winters. Garlic bulbs are harvested in summer, when some of the leaves have turned brown, but 5 or 6 green leaves remain. Finding seed garlic from a source near you is to your advantage, as garlic acclimates to its surroundings, but experimenting with different varieties of garlic is fun and the only way you'll know what works in your particular situation!
Garlic is highly adaptable and can be grown almost anywhere in North America, although ideal soil and climate do give the garlic grower an advantage.