Kerrydw if your watching the parents to pick then u better get the whole litter cause there all from same parents.
I usually look for bigger chest and take a chance. Bigger chest mayb bigger lungs will last longer at a bay if I can't get to them quick.
that's why I raise my on pups usually don't get rid of many until there a few months old and your rite puppys are very hard to pick just grab one