I'm in desperate need of any tips about carving/sculpting cake. Anyone have some good advice? I'll be doing a head shape.

ahhh...a head shape....my very next cake attempt!! i am currently working on another carved cake-a snowmobile for a 4 year old. tips-make sure you have a dense cake, freeze it, carve it, stack it, supports, freeze it, crumb coat it, then final covering.
most importantly when carving i feel is to have some pics for reference, i tape mine to my kitchen window above the counter where i carve for easy reference, using a serrated knife, and carve off a little at a time, step back and look, then carve some more. it's actually not that hard (i did it!!) are you carving a standing head shaped or one lying down? either way i'm sure you will do just fine. just remember to have fun and take photos along the way!!