Balcony gardening is as close to outdoor gardening as flat and apartment dwellers are likely to get. If you have a nice balcony, putting a couple of plants on it will go part way to making up for the absence of a backyard.
One thing that you need to consider more when planting on your balcony than indoors is the weather. Your plants will be exposed to the elements over which you've got no control. And you'll need to be more conscious of the seasons too.
Take note when buying plants and seeds of when they should be planted, as well as their lighting requirements.
You have a huge selection of plants to choose from. Flowers. Vegetables. Herbs. Get to know how much light falls on your balcony, deck or porch and use this knowledge in selecting plants.
If it only gets an hour or two of sun, you're going to have to look at shade plants.
If you have space for a trellis, it can be lovely to grow a vine or other creeper. You can use this as a beautiful backdrop to other containers in the foreground. A trellis can also block a bad view or provide some extra privacy.
In theory, you can use any container you like that fits on your balcony. But do check your building's weight restrictions for balconies. Many buildings have a maximum weight per square metre that you will need to consider. Check your local laws or building's rules to make sure you're not exceeding this.
I recommend using lightweight containers on balconies if you plan to have a lot of plants and if your area has weight restrictions. This means keeping heavy clay pots to a minimum and looking more at nice wooden or bamboo pots. Plastic pots are also a possibility and some of them do a really good job of looking like clay ones. I'm not saying totally ignore clay pots -- they're wonderful and as long as they don't violate the regulations, you have nothing to worry about.
Use the railings to full effect with flower boxes. This gives you extra real estate where you might not have much. They're also great at putting plants at a comfortable working height. Fill them with perenniel flowers and you'll have a wonderful display!
You can buy lightweight soil that's ideal for balconies because it contributes less to the kilograms per square metre restriction in your building or area.
Most balconies aren't that big. So you'll have to make the most of the space you've got available. Use vertical space where possible, for example by using shelving, hanging planters or even a garden wall if you're adventurous!
I've had great success with hanging baskets on our balcony. Many guests have commented how beautiful they are. I find they can turn bland bits of wall into bursts of colour. If you want them to last, look for perrenial flowers that can bloom year-round.
You can also create a tiered structure to create volume. Create two benches, the one at the back higher than the one in front. Put pots on each of these to create an interesting effect that also makes the plants at the back easier to reach.
Attract birds, put up a bird feeder with some coloured sugar water. Balcony gardening really helps bring the outdoors in.