I once read an article about traits in Labrador puppies that indicate whether they will be good guide dogs for the blind, and the direction of the whirls in / near their ears was one indicator of a calm and purposeful demeanor. (justweimaraners.com)
Their bloodlines are usually full of working dogs, which give them the instincts necessary to make a good guide dog. (eyedogfoundation.org)
We've also posted a good guide Dog Food to Improve the Renal Health. (usbones.com)