There are a number of things to consider when choosing a cage for your bird. First and foremost is size. Purchase the largest cage you can afford and maintain. The minimum size should allow your bird to spread its wings fully in all directions. Larger macaws with long tails will obviously need a taller cage. Smaller, active birds will appreciate more room to fly about in their cage. The opening should be large enough to remove your bird without damaging its tail feathers.
Most cages will be made of metal, which is easy to clean and can't be broken by strong chewers. Stainless steel, brass, and aluminum are all good choices. Metal cages with paint (must be lead-free) or epoxy coating can be used, but care must be taken that birds do not pick off the coating and ingest it. Avoid any cage made of unsealed wood, since they will be nearly impossible to disinfect. Scrollwork is difficult to clean, and your bird may catch its claw, beak, or feathers in the nooks. Look for a cage that is sturdy, with no sharp edges, corners, or fixtures, or inferior welding. Ingested metal from flaking, chipping cages can be fatal for birds.
The bars in the cage are very important, as well. Vertical bars are difficult for birds to climb on, so make sure there are at least some horizontal bars on the cage. Spacing between the bars should be appropriate to the size of your bird. They should be small enough that the bird can't push its head through, but large enough that a claw or beak won't get stuck, either. Doors and feed access windows should not be able to be opened by the bird, or must be able to be locked securely with a padlock.
Another important feature of a birdcage, particularly for the owner, is the litter tray. To make cleaning easier, the cage you select should have a slide-out litter tray on the bottom. The tray can then be lined with paper (newspaper with chemical-free ink, butcher paper, computer paper, paper towels, etc.), which can be removed and replaced when soiled. Loose substrates, such as kitty litter or wood chips aren't recommended because of the possibility of ingestion, as well as difficulty in monitoring your bird's waste for irregularities. A metal grid separating the tray from the cage will keep your bird from getting into the soiled litter tray.
Placement of the cage is very important for the health and safety of your bird, especially for the more social species. No bird should ever be put in an "out of the way" room of your house. The cage should be in a place that you spend a good deal of time. It should be free of cold or hot drafts, out of direct sunlight, and have plenty of fresh air circulation. Birds are very sensitive to air quality. This rules out kitchens, rooms above garages, or anywhere else where fumes may make the air dangerous for your bird to breathe.
Inside the cage, provide several perches for your bird to choose from. They should be placed at different heights, away from corners to prevent tail damage if your bird turns around while on the perch. You should also provide perches of varying thickness, so your bird can choose where it is most comfortable. Sterilized tree branches, or their artificial equivalent, are perfect and natural looking. Perches of only one thickness can eventually lead to foot problems in captive birds. You may find perches that are covered with sandpaper or cement, meant to keep your bird's nails trimmed. They also may cause abrasions to the skin on the feet, so make sure this isn't the only type of perch you provide.
Several food dishes and a water container should be provided for your bird. Place them near, but not beneath perches, to protect them from waste dropping in to them. They should be sturdy and easy to clean. Ceramic and stainless steel dishes are excellent choices for food or water. Food dishes should not be large enough for your bird to sit in, and should be shallow so your bird doesn't have to dig through the food (i.e., throw it on the floor) to see what you've given him to eat. Water dishes should have large opening so your bird's head cannot get stuck. Your bird may also use this dish for bathing if you buy one big enough, and if so, it should be cleaned at least twice a day. If you are using a sipper bottle to provide water, choose one with an appropriately sized metal drinking tube. Glass drinking tubes can be cracked or broken by large beaks. Deep scratches or chips in any food or water container can trap germs, and should be replaced. Otherwise, they can be cleaned daily in hot, soapy water or with a mild bleach/water solution (rinse well!). Two or more full sets of dishes will allow you to swap sets, and give you more time to clean them. Food skewers with flat points (or capped with cork) can also be used to hold foods too messy to be held by foot, or can be used to hold your bird's mineral block or cuttlebone.
Play stands may also be available with your cage, or separately. These are good ways to keep your bird entertained while out of its cage. Some can be removed and placed on tabletops around the house, so your bird can check out other rooms. Play stands, or T-tops, should come with a litter tray, food and water dishes, and a few toys.
Last, but not least, your bird will be much happier and healthier with the addition of some toys to its cage. They relieve stress, and can actually be therapeutic as well as fun. There are many different kinds available, so try out several to see which your bird enjoys. Some birds love bells, others enjoy anything they can throw in the air and retrieve. Some like to hold their toys, others prefer toys that hang from the cage ceiling. Be sure to choose only toys suitably sized for your bird. For birds that enjoy chewing, try acrylic or wooden toys. For birds that have a tendency toward feather plucking, try a rope or cloth toy. Always inspect the quality of the toy before buying it for your bird. Avoid toys with parts that could be chewed or pulled off (or remove them yourself). Cloth toys should not have loose strings that could wrap around a bird's foot or neck. And don't overlook household items. A good rule of thumb, if it would be safe for a baby to play with, then it's probably safe for your bird (but don't forget about beak strength). In fact, baby toys make excellent bird toys.
To keep your bird healthy, it is vital that you keep its cage and accessories free from germs. Daily: change the litter tray, wash food and water dishes, spot clean any food or waste on the cage or perches. Weekly: thoroughly wash (with mild soap) cage, perches, and toys. Monthly: disinfect cage, perches, and toys with a pet-safe disinfectant or 10% bleach solution and rinse very well.