
My bitches have always weaned their pups themselves. As the teeth get sharper (ouch!) and the pups get stronger, and I'm giving the pups solid food (and so is the bitch) they feed less and less. At 5 weeks she feeds them standing up, and pulls away when she's reckons they've had enough! At 6 weeks she'll still 'top them up' occasionally, but by 8 weeks all her milk has gone and everyone is happy and stress-free.
4 weeks is very young to assess character - that won't start being evident for another week or so, but for health, a shiny coat, no sign of fleas/lice/scurf, bright eyes (no sign of discharge), clean, sweet-smelling ears, correct 'bite', sturdy body, and if male, 2 descended testicles (again, at 4 weeks these are unlikely to be evident!)
Good luck!
:)