Small gardens require smaller beds. Small beds take less work to prepare, plant and maintain. Take advantage of unused garden space in a neglected corner by tucking in a small garden bed. Spacing plants closer together in small beds is possible if the soil is rich you follow a regular fertilizing schedule. Be vigilant about protecting your garden from pests.
Select plants that stay compact. One bushy big plant will overshadow all the others and deprive them of sunlight. Dwarf varieties of flowers are better than the full size. Try dwarf snapdragons, zinnias and cosmos.
Plant the tallest flowers in the middle of an island bed. That way when the sun moves from east to west the flowers on either side of the tall flower will receive sun for at least part of the day. Plant the tallest flowers in the back of the bed for a border that is backed by a wall, fence or house.
Put the flowers that are mid-height in front of the tall flowers, or in case of the island bed, around the tall flowers. Good choices would be marigolds and petunias.
Edge the bed with short, spreading plants like moss roses, bacopa and lobelia.
Keep the size of the flowers about the same with the exception of plants that have many small flowers like sweet alyssum. A small bed looks out of proportion with huge flowers like sunflowers surrounded by small flowers like daisies.
Vary the shape of the flower for visual interest. Use the round shape of coreopsis, contrasted with the cup shapes of mallow and the feathery plumes of snapdragons.
Follow the same principal of tall flowers not blocking the light for the shorter flowers when planting vegetables. Put tall vegetables like peppers and eggplants in the back of the bed, with shorter vegetables like leafy greens, carrots and beets in the front.
Grow as much as possible vertically. For example, pole beans are a better choice than bush beans. Plant and stake indeterminate tomatoes rather than growing bushier determinate varieties. Cucumbers stay out of the dirt and grow straighter when they grow up a trellis.
Select vegetables you really like and that taste better when grown fresh rather than purchased at the grocery store. Plant vegetables that produce all season long like squash, rather than those that produce one main crop all at once like corn.
Plant vegetables that don't require a lot of space to produce. Fresh corn is a treat, but corn is a space hog. One stalk requires 3 square feet of space to produce one ear of corn.