The first task of any downsized gardener is to assess the damage- er, I mean assets, of course.
1. Measure: Take a small sketch pad and measuring tape out to your porch, balcony, or two square feet of roof and commence to measuring. Map out the floor plan of your space first, then go back and fill in the heights of the walls (if any) and dimensions of any special features, like doors, windows, or railings.
2. Draw A Plan: You'll want to have one sheet of paper with your garden floor plan on it. It's helpful if this paper contains measurements- then you can stick it in your pocket and take it to the garden center with you- but steer clear of making too many notes on it. The clutter will make it hard to think clearly. When you're ready to play around with inserting and moving around containers, though, do what architects do: get a roll of tracing paper, lay a piece over the master plan and let your imagination run wild.
3. Assess Conditions: This includes observing and writing down how much direct sunlight each area gets (I divided mine into zones 1, 2, and 3 for the north, east, and south railings and wrote it how much sun each gets on the plan- what a dork!), how much rain or gutter runoff each area is exposed to (I taped construction paper onto each railing during a thunderstorm to see how wet it got; maybe not so scientific, but helpful), and if there are any surrounding trees or plants that, when in bloom, might create shade for your containers. Is it really windy up there? Any specific conditions you'll have to work around? Jot those down, as well.
When I finished all of this, I found that the East Rail gets five to seven hours of sun a day, the South Rail got only one to two hours of full sun a day, and that the North Rail got no direct sunlight. This works out well for me; there are plenty of plants- ferns, chives, and parsley, for example- that do well in total shade. My North Rail can support that. The sun-loving vegetables and fruits are going onto the East Rail, and some part-shade/part-sun plants can dominate the South Rail. Luckily the sunny East Rail is the longest.
It's so important for those of us engaged in a fight for sun and space to look outside the typical to get more of both for our container gardens. I can get even more veg up front on the East Rail by utilizing hanging baskets. There are enormous brick posts at each corner of the porch; could those somehow be made to support a basket or two on their faces?
When looking at your space, think about growing up. Think backwards. Think forwards. Think vertical and horizontal. Could you grow anything upside-down? There are special hanging planters designed for just that purpose that are supposed to work wonders with tomatoes.
With so little space, you're going to have to use your imagination. Just think, though, how much more impressive the final result will be because of it!