I disagree with "don't pick the quiet one" . I picked our first pup - dh wanted the one that bounced all over him but this one was my choice. I picked the girl at the back who looked at me, and was clearly assessing what was going on.
She was an amazing dog. When we had Dc they learned to walk holding onto her, she would go stand by the child clinging onto the sofa and wait until they transferred to her, then slowly walk round the room. She was very smart, picked up commands easily, remained gentle, quiet and thoughtful all her life.
She was supposed to be "my" dog - but the minute we got her home it was clear she was dh's devoted acolyte. She would do anything I said but if he walked off in the other direction she would follow ...... we were in an obedience competition once, doing ok, I'd told him not to be ring side - but half way through she spotted him in the distance and just shot off to be with him.
A year later we got a second dog, his choice, he did choose the lively one, and she was bonkers, lovely but dim. She decided she was mine 🤷🏼♀️
We've not always had a choice with pups - but last time I got a working bred gundog and the breeder narrowed it down to two that she thought would fit in well with me. Again, I chose the quieter one. She is a bit more anxious than my first, but I don't think she's had the same opportunities for socialising - and it's not a bad thing that she wouldn't wander off with a stranger, or approach them on walks.