Seattle Tilth's community-garden plots are 10 feet square, a nice size for novices if you can spare the space. Create a horseshoe-shaped bed within it, and you'll be able to reach everything from the center or perimeter.
In a larger garden you'll probably want rectangular or curved beds with paths between them. Beds 2 to 4 feet wide generally work best. "Just make sure the bed isn't more than twice the length of your arm," says Pencke with a laugh. Make main paths at least 3 feet wide so that you can get a wheelbarrow through.
In a small garden it often works best to divide a bed into square-foot sections. Devote each one to the number of plants that can use the space efficiently. So you might put in nine bush beans, since they need about 4 inches between plants, or 16 onions, spaced 3 inches apart. Once you've settled on a tentative site and size for your garden, sketch various plans for planting beds and paths on paper to help you choose a design.
Shown: Lettuce grows fast but turns bitter as it sends up a flower stalk. To be sure you always have young leaves to harvest, plant a few new seeds every few weeks.