Even the smallest of spaces can produce a lot of vegetables when you use intensive gardening methods. Your first consideration in a scaled-down garden must be to prepare and enrich the soil, since a large number of plants in a small area will compete for nutrients.  

When planning your garden, emphasize vertical crops. Peas, pole beans, cucumbers, some melons, and some tomatoes are vining crops that actually perform better when they are kept off the ground. These can be grown on an attractive trellis, tied to stake, or trained to follow twine that is anchored to the ground and an overhead frame.  

Also, to reap as much harvest as possible from each plant, choose compact varieties or prolific producers, for example, leaf lettuce (cut and come again) continue to produce through the spring and early summer, require comparatively little room and can be used in small spaces, Dagan Brussels Sprouts yield an early, bountiful crop. As a rule, the smaller the fruit the more the plants tend to produce, so make most of your selections from small varieties such as cherry tomatoes.  

Avoid the temptation, though, to plant too many hugely prolific vegetables, such as zucchini. When laying out the garden, make use of succession planting and intercropping to maximize your growing space.