As mentioned above, the height of the cage is not as vital as having room to fly horizontally, so a long but shorter cage is acceptable. While experts vary in their recommended minimum size, it a good idea to get the largest cage you can. 30 inches long, by 18 inches high and 18 inches wide is a good sized cage for a pair of zebra finches. If you are going to get a larger group, you'll need an aviary or flight cage. This can be home built, but keep in mind that excellent hygiene is a must so any cage should be easy to clean. Wire spacing should be 1/4 inch to 1/2 inch.
Furnishing and Toys
Supply a variety of perches, but make sure the cage is not so cluttered that the finches cannot fly back and forth (keep an open flight path through the length of the cage). Use a couple of different sized dowels and try to add some natural branches as perches too, perhaps angling them to provide further variety so their feet are not always holding onto perches in exactly the same way. Small clip on perches can be used for some of the perches, and are nice since they do not span the whole cage and offer a little privacy in an aviary situation since only one or two finches can sit on one at a time. If possible, provide some plant cover at the perches to allow for privacy (also more important if keeping a group). You can use silk plants or non-toxic live plants.
Swings and ladders can also be provided, although ladders are more likely to be used as perches than for climbing. Small bells or hanging toys can also be included, although finches are generally not very interested in toys.
You'll want the finch cage in a quiet secure location in your home (although in warmer climates finches can be acclimated to outdoor aviaries). Avoid direct sunlight (overheating risk) as well draughts or being to close to heat or air conditioning ducts. Finches do not crave social interaction with people so unlike parrots do not need to be in a busy social part of the home, and in fact will probably be less stressed if kept in a quiet corner.
Water and Feed Dishes
Provide fresh drinking water daily. Some keepers prefer tube style water dispensers, while others use dishes either attached to the cage (with perches for access) or on the floor (place away from perches to reduce soiling with feces). Whichever you use, make sure there is always a supply of fresh clean water available, and clean water dished daily.
Food dishes can also be placed on the floor (also not under perches, of course) or attached to the side of the cage. Again, these need to be cleaned daily.
A shallow dish of water should be provided several times a week for bathing. The water in the bath should be clean so remove the bath water as soon as it becomes soiled.
Some people use full spectrum lighting for their finches. This is helpful especially in controlling molting and breeding behavior, but isn't strictly necessary for the average pet zebra finch.
Next: Feeding Zebra Finches