When it's finally time to go pick out a puppy, what do I look for?

I'd like a mellow blocky girl. Can you tell which ones are more blocky at the puppy stage or do you have to wait until they are full grown to really know? Also, is it true that the more mellow pups will let you turn them over on their back no problem? I'm wondering if that only applies to a certain age too...

Any advice at all would be helpful.

Mellow or not a well bred socialized Lab pup will allow you to hold it on its back.

As for wanting a mellow girl I would be sure and tell the breeder this as she knows her pups best after raising them for 8 weeks.

Heads are tough. They can change so much as they grow. Just like the rest of the pup. What you keep as a breeder may not turn out to be what you thought it was going to be.

I would find a breeder where you like the look of the adults, and then have an open discussion with the breeder you pick about what you like to do, what your family is like, and normally they will pick a puppy for you based on that.