Before you plant anything, plan out where things are going to go as this will optimise the space and make things easier when you go to sow your seeds. What you plant will depend mainly on the size of your space, but you may be surprised by how much you can get in to the smallest of balconies (click here for proof).
On the following pages I’ll run through several of the more popular crops and briefly outline their growing requirements and the minimum container depth they need, to help you choose which are most suited to the space you can offer. If a particular crop needs a lot of space in its own pot or is best suited to a raised bed (cabbage, for example) don’t let this put you off growing one on your balcony. Just be aware that it will take up the same space as, say, a few tomatoes, some runner beans and lettuce – all of which require much less space and could all be grown together in one pot.
I’ll also suggest some planting schemes for small and larger spaces, briefly look at crop rotation (important if you are growing in raised beds), and suggest which plants grow well together and which combinations to avoid. Tomatoes, for example, can be grown together with most herbs and lettuce in the same pot, but should not be placed next to a potato plant as the two are very closely related and will pass blight, a fungal disease, quickly between them if either gets infected.
If you want to get into this in more detail than I can offer, I recommend The Edible Container Garden: Fresh Food from Tiny Spaces by Michael Guerra, Complete Book of Companion Gardening by Bob Flowerdew (the section on edibles is short but excellent), The Permaculture Garden by Graham Bell and The Alternative Kitchen Garden by Emma Cooper.