If you buy organic garlic bulbs you can separate the cloves and plant them with success. Plant them like onions and be patient. I found it is best to plant them in a pot as you can control the water better and also take them in if it freezes where you live. Sometimes you can find garlic for planting in a farm feed and seed store where they sell onions by the bundle and seeds by the ounce...hard to find these stores anymore but worth looking.
Basically, you can purchase garlic bulbs at any of your local grocery store particularly in the spice section. Garlic is normally grown from cloves rather than seed. Find out the steps on how to grow it on http://www.ehow.com/how_4477992_grow-garlic.html.