You want a cage that offers a lot of room for your bird to play and fly around in. They need to have ample wing exercise. You also want to keep in mind how much bar spacing you allow, so you don't hurt the bird's feet.
I personally like this cage: http://www.drsfostersmith.com/product/prod_display.cfm?c=5059+10346+23415&pcatid=23415
The reasons I like this cage: It has coasters, therefore, you can move the cage easier, should you need to move the bird away from a window so it doesn't get sick from a draft. The cage has a grate that is removable and easy to clean. This way, your bird doesn't touch any fecal matter or food that has been dropped. The cage has 1/2" bar spacing. Very easy for your bird to grasp yet the cage itself is sturdy, so the bars won't bend. The cage offers a perch up on top, so the bird can spend time out of the cage,which is important to do with your bird. :)
I hope this answer helps you.