Shipping Birds

[NCSUBird]

I was wondering what the general consensus is on shipping birds (finches and parrots both). I was searching for a new male canary recently (I just got him today ) and I found a lot of breeders that would ship and a lot that wouldn't. I decided to go with a local breeder so I could pick out the exact bird I wanted in person. If, in the future, I was interested in shipping a bird (there are some BEAUTIFUL ones....halfway across the country), what would I need to know?

Legal methods? (I saw some dispute on whether or not it was legal to ship canaries USPS, even though finches are legal)
Preferred methods?
Safety?

If anyone here sells and ships birds, I'd love to hear that perspective as well.

Thanks a bunch!