Planting and growing garlic, a member of the onion family, starts at the store, when you purchase your bulbs. There are really two different types of garlic: softneck and hardneck. Softneck garlic grows in a variety of climates, and is the most abundant in grocery stores. Hardneck garlic grows larger and is easier to peel; this is a popular type of garlic for chefs because it has a variety of complex flavors.
In addition to the two main types of garlic, there are a lot of varieties or cultivars. Garlic will grow in a variety of soils and climates, but ensure that the variety that you purchase is well suited to your climate. For example, only hardy varieties that are adapted to northeastern climates will grow well in the northeastern United States.
Garlic planting occurs in the autumn; this is completely out of synch with typical planting periods. The best time to plant is after the first frost in October but before the end of November. Garlic requires a cold treatment of about 40 degrees for two months in order for the bulbs to begin growing. If you want to plant garlic in the spring, refrigerate the bulbs or plant them early enough in the spring for them to experience that same period of cold treatment.
Where and how you plant the garlic depends on where you live, but some aspects can be constant. Plant the cloves with the root end facing down and the pointed end facing up. They should be planted about six or eight inches apart. If you live in colder climates, you should bury the roots about three or four inches deep; in warmer climates, about two inches deep should suffice. If you are worried about the cold, you can mulch around the roots to help the soil retain its moisture.
Finally, when growing garlic, remember to weed vigorously; garlic is not very competitive, and will succumb to more aggressive weeds. Irrigate your garden well and don't forget to label your garlic varieties.