1. Every clove becomes a bulb, so take as many cloves as you plan to harvest full bulbs. You can just use garlic from your greengrocer, dried or even ones you kept too long in your cupboard.
2. If you have a garden, or a little piece of soil situated in a sunny place, just prepare the ground by digging it a little. No extra fertilizer is needed.
3a. Make a little hole of about 2,5 cm deep and put a clove with the narrowest tip upwards in the cold earth. Put the next ones 15 cm further away. Be careful not to push the cloves with too much pressure in the ground. Once planted, do not replant the garlic.
3b. Growing garlic in a pot on a balcony is also a good possibility. It requires the same preparations as described in the previous steps. The only negative point of growing crops in pots is the bad draining, so make sure the rainwater can get away, and don't let the plants dry out.
4. At the end of the summer (just let nature do all the work and watering), the green stem leafs will turn yellow, dry and begin to droop. When this phase is complete, you can carefully dig up the bulbs and leave them to dry in the sun. If it rains, dry the garlic under a shelter.
5. Hang the garlic in a dry and cool place for storage. Garlic will stay good for a long time in this way. Don't forget to save some cloves for next year!
Edit 22-2-2013: as Anonymous pointed out below, October and November are also perfectly good to plant garlic.