I have a gag strip that updates VERY frequently (I'm aiming for daily updates, believe it or not), so for that reason I have to draw as quickly as possible, so I pretty much always draw lineart first.
To draw heads, I draw a circle, then I draw a half-oval thingy underneath the circle for the jawline, and then I draw the ears, the hair, and the body. After that I erase any extra lines, fill in with colors, and then draw the eyes and facial features.
Weird technique, I know, but hey. It's my own way of doing it.