A calm Pug that does respond to you when picked up is what you should be looking for. Listen to the breathing for any signs of labored breathing or rasps. If the breathing is clear, take a look at the eyes. They should be bright and clear without an excessive discharge.
With 2 or 3 puppies now left for you to decide on, take a look at how each one responds to you and how they respond to each other.
Wiggle a toy in front of a puppy or whistle to him or her and see if the pup shows natural curiosity. The one for you should come over to you to investigate. The pup should sniff around your hand, perhaps lick your hand and even nibble a bit (although this will have to be dealt with once you bring him/her home with teething
Allow the whole litter to play with a toy. Take notice of the ones that seem to be bossy and the ones that seem to play fair. Take note of the ones who cower in the corner if the others fight for the toys.
You will want to choose a Pug puppy who falls somewhere in the middle. This will ensure you have one that has a calm, yet curious personality
Finally, when you have it narrowed down to 2, do not feel rushed. Take time to sit down with each and talk to them. Does the pup look at you when you talk? Does he or she keep their tail high or wag the tail (to express happiness)?
At this point, you should get a good feeling about which puppy is the one that is meant for you. Please remember, that just because you have an appointment to pick up a dog does not mean that you must go home with one.