I read an awesome blog that I would recommend to Urbanites about Small Square Foot Garden Design . Here is a small exerpt of that post.
"A Small Square Foot Garden Design
is typically defined by a 4 foot x 4 foot square that has been seperated into 1 x 1 squares. This makes a total of 16 squares. This is a very methodical approach to companion planting. Companion planting is planting several different types of plants next to each other that compliment each other in many ways. They can give soil nutrients that the other needs. Another reason to square foot garden is the insane amount of produce from one square foot garden. If you create a matrix of these four foot squares, with a few feet in between, you can have convenient walkways between very efficient beds.
The typical garden begins with a 2x4 or 2x6 square frame, and then using a .5x1 lattice structure (or my favorite: PARACHORD) to seperate each into the 1 sq ft sections. Each of these can hold a precise amount of a vegetable, depending on the vegetable. The below photo shows how plants can be placed in the 1 foot square. Each Big square is 1x1 feet."
Obviously, there is much more to the post, but all you have to do is follow the link.
Small Square Foot Garden Design