I'd say that GENERALY, you can see the basis of their temperment. Watching the puppy interact with the litter is a good clue. If you see that one tends to kind of beat up on the other pups, that's probably going to be a more rambunctious, possibly dominant personality. If there's one that seem to chill in the corner more, that's a more submissive, quiet dog. I know those seem obvious, but things like that can help.
What I've always done after kind of "weeding out" those more "extreme" pups one way and the other, is let the dog sort of choose you. Hold and play with the others that catch your eye and see which one you seem to "bond" with the most.
When I was picking from Alice's litter - I was torn between 3. I held each one, one was shaking scared really bad in my arms, one only wanted to chew on my hoodie (lol), and Alice just kind of seemed relaxed in my arms.
My Beagle - out of a litter of 8 on my uncle's farm, she was the one who came over to great me when all the others were too busy playing with each other to care that I was there.
My Akita - out of 6 puppies in an Amish family's horse barn, 4 of them were barking at me and wouldn't come near us and one peed on me out of fear when I picked him up (lol). Miya seemed mellow, not too scared and was interested in me.
All three of these dogs proved to have the temperment I felt I saw with their litter and have been a perfect fit for me. Of course they go though some changes as they age through puppyhood, adolescence and adulthood, but the
basics of their temperments were noticable right away with observation.
If you feel like you have a "bond" with the little girl you're thinking of buying (not just based on looks), I'd say that's the perfect way to choose
