For the most part the vibe is the best. You just know. As for picking up others, i feel better if they have a pack, but it normally doesn't bother me either way. I also try not to get too pissed when a car full of little ones shoot me down. On that note, single mothers driving alone are always picking me up, I generally travel with another person too.
Then the pitt thing, man there is a bond between a traveler and their dog. You just have to be the dominate. To my dog, I know she could fuck me up if she wanted, but she trusts me and listens because we are, to her, a pack.
That and I really have to defend the pitt. I'm tired of people loving other breeds that are known for a bad rep, and turning around to sign off the life of somebody else's bad named pup. Shit, chow's freak the hell outta me, but I don't want the breed gone. I just try harder to be comfortable around them. It's not the dog's fault it's alive, just like it's not a person's fault that they are.