
I use the Volhard's method of puppy assessment at 49 days old. It's useful to pick out your own pup, and to aim new puppy people towards a suitable pup, but you can't always convince the new owner!! Nor have that much control over their future training, of course; only that of your own pup.
I find it particularly useful for picking the better potential workers.
Its on
http://www.golden-retriever.com/pat1.html
Jo and the Casblaidd Flatcoats