>the one that's bouncing all over you isn't necessarily choosing you, but does that to everyone!
There is the other scenario that the puppy running up to you had just woken up, whereas the one at the back is the one that has been running around for the last half an hour and is now tired ;-)
This is where you try to help the potential owners by telling them which of the puppies is most suited to their temperament. A good breeder can put the right pup to the right owner, but it is still up to the owner to choose the puppy, so long as you don't think that it is very definately the wrong pup for them.
Oh, and also, I sold a puppy to a family some years ago where the wife was buying said pup for her husband as a surprise (yes, I know ;-) ) anyway, the husband had had a dog of my breed before but his first wife had made him get rid of it. They were over the moon to get one of mne. About 6 months later I got a phone call saying that they wanted rid of the pup as it was jumping up on everyone and peeing everywhere. She returned home with me and there was no real reason but we believe that they had removed the waterbowl so that she didn't pee so often. I won 't make the same mistake again. Go with your gut feelng, it's usually right.