Don't you just hate/love it when you come across a wonderful tutorial video that you really wish you had seen earlier/are really grateful for?
Here are two, by Ryan Kittleson -
Modelling a Human Hand:
Modelling a Human Head:
As you may have figured from the addresses, these tutorials focus on getting the basic edge flow right to allow for the most natural looking deformation (for blendshapes, etc). What surprised me is how few edge loops are needed to create almost a complete human hand, fingernails and all. The face... much more difficult. I'm still working on it.