Check labels and descriptions for plants and seeds for sun and shade preferences so you get the right varieties to match your sun exposure needs. Full service nurseries and garden stores usually have trained staff who can answer questions and make suggestions. Variety descriptions in catalogs and books also can give information in making plant choices. Another important guide is what you like to eat. With limited space, you will want to avoid varieties that grow large or sprawl.
Almost all gardeners want to grow tomatoes. Tomatoes come in two types. Determinate varieties have short stems and a bush type of growth. Indeterminate varieties have long stems and a vining type of growth. Almost all tomatoes can be grown in containers if supported by a wire tomato cage. Vining varieties need a 5-foot cage or support trellis. Tomatoes like lots of sun and reflected heat and light. So a location near a south- or west-facing wall or fence is good.
Lettuce is another popular vegetable that can be grown in containers. Leaf lettuce goes from seed to harvest in about 60 days but has a relatively short harvest period. A second and third planting can be made at three-week intervals to spread the harvest. Cucumbers sprawl but can be trained on a trellis to maximize space.
Carrots, beets, onions and similar vegetables can be planted in blocks rather than rows to maximize production. Seed scattered over a 1-foot square will produce as much as a single row 6 feet long.
One of my favorite sources of seed adapted to the Northwest is Territorial Seed Co. (territorialseed.com), which also has a very nice catalog and seed racks in some full-service nurseries and garden stores.