Head Sculpting 
Each base mesh only gets you so far. The real work begins from sculpting the looks for the character, starting from the head.
Start from the most obvious places and most prominant features.
Build the larger shapes first and then work the smaller details in with multiple passes.
Try to stay away from using too much symmetry. Even though the base mesh would be symmetric, the character using the bash mesh certainly doesn't have to be, and when looking at any reference image of people's faces, you'll find non of them are quite the same from either side of the head.
This is how characteristics are created. Let the face be a bit ;off; from the symmetry.
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