Here is some skin shadig tips from my making of tutorial.
Scale of model is one of important things that must be well tuned becasue subsurface scattering weights relies on scale
If you are not sure how to adjust scale of your model in maya or max here is tip.
First load your model and apply fast skin material on to it.
Place some point light in front of your model and one point light behind model.
Point light behind should shine through your model in red color when rendered.
That red color comes from back scatter component of sss fast skin shader.
Now adjust scale of your model or even better scale conversion parametar in material until that red color only shines through the ears and some of it through the neck of your model. (IMAGE 2)
That way you will be sure that your scale is correct since fast skin shader comes already tuned for optimal results.