I like to keep records on my newborn puppies, so that I can refer to them as they grow up. Quite often the observations made at birth carry through to 8 weeks of age and adulthood.
One of the things that I do is: I support the head with one hand, and support the body with the other and let the front and rear legs just drop. The puppy needs to be tired and still while you are doing this. Once the puppy is relaxed you can see where the legs are going to drop, whether they will be straight or turning in or out, and how far apart they are. It is easier if you do this in front of a mirror.
On the chart I have a spot where I can draw a diagram of the puppy, if I wish, or make notes.