
At five weeks I often have an idea of which ones catch the eye, and the definite no's.
I like to choose at 7 weeks, though people who wrote the Puppy Puzzle say 8 weeks no more than 3 days either way.
Old time breeders in the UK of my breed said 6 weeks, but I find some pups may not have got leg yet and others have and as adults both turn out the same for leg so I like 7 - 8 weeks.
After 10 weeks had I not already decided I find that I would not be able to make up my mind as their proportions change with much more leg.