Balcony, porch, deck, stairs, roof, planters, neighbors yard, etc. These different areas provide different microclimates and other considerations. Wooden structures can often be cooler due to air circulation, while stone or concrete can be warmer and hold on to heat. Light colors will be cooler while darker colors can greatly raise the temperature. Higher temperatures can be good for some plants, but bad for others. A shingled roof is almost a desert-like environment; the only thing I've grown there is rosemary and succulents. Your garden may be in a different “zone” than maps suggest. The direction that your garden faces will also have an effect, as will the presence of a roof over your plants. In the northern hemisphere, balconies facing to the north will receive little light while balconies facing to the south will receive a lot of light. Solar intensity is highest in the middle of the day so an hour of sunlight in the early morning is not worth the same as an hour in the afternoon. This is actually good for some plants because some plants can't handle the highest intensity light. If you annex a little chunk of a neighbors yard, you can grow some things that you may not have space for, or things that dont grow well in planters. You want to make sure to keep it tidy and nice looking, and focus on lower maintenance plants so you aren't constantly in their yard. One last thing to consider for planting areas is if you are in an old house, you may have lead exterior paint. When it flakes and falls into your soil, that lead stays there indefinitely. Lead will not be taken up by plants, but plants that grow underground, or close to the ground like leafy greens can get lead dust on it that you don't want to eat. If you know there is lead in your soil, plant things that aren't close to the ground (e.g., tomatoes) or ornamentals, and wash food well before eating.

Edible vs ornamental

Balcony plants will likely need some water unless you live in a cool/wet area, or have fairly large planters. You can water by hand, but there is risk if you aren't consistent or travel and don't have someone to water for you. You can set up irrigation without too much trouble if you have a hose spigot (link to irrigation post). Plants in the ground won't need as much water as plants in planters, and heavier planters need less water than lighter or smaller planters. Plastic pots in particular can dry out quickly in direct sun because they heat up quickly. The soil itself can also help retain water. Make sure to either buy potting mix, or make your own instead of just using whatever dirt you find.

Soil is important to get right for potted plants. You can buy potting mix from the store but it may be more cost-effective to make it yourself. The main difference is that potting mix is often fluffier than regular garden soil because it has a much higher organic content in addition to ingredients like perlite or vermiculite which provide aeration and water holding capacity. Ingredients like peat moss are a non-renewable resource (actually a fossil fuel), so I would avoid it if possible. Additionally, peat moss actually repels water once it gets dry, which can make it difficult to actually water your plants.

There are very many pests that can be either general or specific to plant varieties. You will likely need to do research for your specific plant to know what your pests are. As a general approach, keep an eye on your plants, especially at the beginning of the season. Look at all parts of it to see if you can see anything on the plant, including eggs and frass (poop). Do not just blindly kill whatever you find, do some research to figure out what you are looking at. A larva ladybug can really help get rid of aphids, so you don't want to accidentally kill it. There's a lot more beneficial insects than you'd think. Tomato hornworms can eat a tomato plant very quickly, but if you see what looks like eggs sitting on the back of a hornworm, those are parasitic wasp pupae, and the larval just finished eating the hornworm from the inside out. If you let it sit on your plant, you'll get dozens of parasitic wasps that will hunt down any other hornworms. Try to avoid pesticides, and also be careful what “home remedies” you find out there, cause lots of those do nothing. It's frustrating to get aphids on your cilantro, then see a “home remedy” that says that cilantro is supposed to drive them away. Lastly, some plants may just be a challenge in your area for pests. For example, if you have a lot of wild brassicas (like garlic mustard) in your area, there's going to be more pests that eat them, in addition to your brassicas (cabbage/mustard family).

• Many planters/pots are made of plastic. They are cheap and lightweight, which can be handy for hanging baskets or plants on railings. However, lightweight pots may be able to heat up and therefore dry out quicker. If you would like to repurpose plastic, be sure that you are using something that is UV stable. Many plastic totes, etc, that you may want to repurpose will become brittle and rapidly break down in sunlight. You can paint plastics to block UV. Often, transparent/translucent/white plastics are not as UV stable while plastics made to handle the UV will be opaque or even black.
• Check the resin identification code (counterfeit recycling symbol used by plastics industry to make people think their products are recyclable) to see what type of plastic it is to see if it's food safe and UV resistant
• Convenient recyclable options include HDPE barrels (preferably foodsafe), hdpe buckets (you can ask for used frosting buckets at a bakery), IBC totes (very popular for aquaponics ), retired/scratched up restaurant bulk food containers (cambros), and concrete mixing tubs (very nice as a portable potting bench). Be sure to make holes in the bottom to allow for drainage.
• Plastics to avoid: probably many

• Cedar is a common planter material for its rot resistance
• If making a diy planter, be sure to account for how the wood will break down over time. Nails will loosen due to moisture.
• Make sure not to use treated wood, they can contain a lot of harmful compounds.
• Pallets can be either heat treated (safe) or chemically treated (not safe), so be sure to check

• Since masonry is heavier, it can sustain temperature and moisture better than other options.
• Terra cotta is a very traditional pot material that allows moisture and air to leak through
• Glazed ceramics do not allow moisture to leak through. Make sure that if there are only holes on the bottom of the pot that they aren't blocked by the surface they are sitting on
• Cinderblocks (concrete masonry units) are cheap, and they can be turned on their side to act as cheap planters.