Each of the four directions is associated with an element. North is connected to earth, east to air, south to fire and west to water. To plant your elemental garden, figure out which plants are connected with those particular elements -- and this will vary depending on where you live. For example, earth is associated with stability and security. Why not plant some herbs there that carry the same associations? Bryony, cinquefoil, honeysuckle, and pennyroyal* are all related to earth.
For the east section of your garden, which is tied into the themes of air, use plants connected with inspiration, wisdom and knowledge. Sage, marjoram, mugwort and members of the mint family are perfect for this quarter of the circle. In the south, select plants related to the passionate qualities of fire, such as basil, betony, rosemary and rue. Finally, the west quadrant is where your water-related plants should go -- hyssop, yarrow, chamomile and ivy will do well in this section.
* Be cautious when selecting plants for your garden, and be sure to do your research. Some forms of pennyroyal are toxic and can cause miscarriage in pregnant women, and can be potentially fatal if ingested by small children.