Round cages are not recommended for parrots, small hook bills , canaries or finches.  

Cages for hand tamed birds should have a large training door, to reduce stress when the birds steps up on you.

Older or rusty cages are risky because of possible toxins, such as lead or zinc in the metal.

Introducing a very large cage too early in a baby birds life can cause insecurity. A small overnight sleeping cage is recommended for young birds in the months after weaning.

The accessories in your cage and how they are arranged are as important as the size of the cage.

Starter kits are not recommended. Provide the complete proper environment for your pet when you first set up.

Some feel that all the bars in the cage should be horizontal. (Perching birds need many diameters and textures of perches, not only metal bars to climb on.) Most cages today have 2 sides vertical and 2 sides horizontal.

It is commonly thought that a tall cage provides a large environment. Width is more relevant to a bird to create room for exercise and play.

Choose a cage the right size for your bird, not your living room.

A more expensive surface such as powder coating will reduce cleaning time.

Beware of over flashy colors such as brass, chrome or bright colors

Consider how long will your bird be in the cage each day. If a normal work day, provide adequate space for exercise and fun.

If you plan to move the cage often, make sure it is on casters.

Imagine the cage space once you put in perches, ropes, toys platforms, etc. Make sure it is large enough to accommodate the necessities.