I would have to see your setting for specifics... Erlik is right, and all I can really add is That I usually set diffusion around 80% and ambiance around 20% for a starting point. A wee bit of bump can really help things, a very low specularity and you might try reflection but keep it very low....sometimes it gets a good effect. Check your sky settings, it is advisable to turn the shadow intensity down, this can help the way skin looks.