Buy garlic bulbs at the nursery in late fall or early winter (it's unlikely you'll find started seedlings). You'll plant cloves directly in the ground about six weeks before the soil freezes. In mild climates, plant in January or February for harvesting in late summer or early fall.
Choose a garden site that gets full sun. Though garlic will grow in soil with any pH from 5.0 to 8.0, it does best in the slightly acid range (6.2 to 6.8).
Dig to a depth of 8 to 12 inches, and amend the soil with plenty of compost to ensure the ideal combination of fertility, good drainage and moisture retention.
Remove all traces of weeds; they'll easily win out over garlic's grasslike foliage.
Plant only the largest cloves from the bulb, and discard any that are pitted or tinged blue-green - both are signs of mold.
Set unpeeled cloves, pointy end up, 2 inches deep and 5 inches apart. For giant "elephant" garlic, increase the depth to 3 inches and the spacing to 10.
Top-dress the plants with compost, and mulch to retain moisture and deter weeds. Mulch again after the ground freezes to protect plants from the cold.
Remove the mulch in spring so the sun can warm the soil, then add a fresh layer when new growth begins. To ensure large bulbs, cut back any flower stalks that develop, and spray young plants with compost tea (see "How to Make Compost Tea") once or twice during the spring.
Provide an inch of water a week until the foliage turns yellow or falls over - indications that bulbs are nearing maturity.
Clip garlic leaves to use any time, but remove no more than 1/4 of a plant's top growth or you'll reduce bulb size.
Begin harvesting bulbs when about 3/4 of the tops are yellow.