I don't trust artists interpretions or standard formulas so I sculpt what I see.

If it looks like the photograph or fits the blueprints, it must be right.

The only thing I have to worry about then is that everything is in scale with each other, i.e the 1.87m tall man is actually 1.87m tall in Poser, the 5.20m long car is actally 5.20m long, and so on.