Well bump maps work through shades from black to white, white representing height and black representing depth....in the middle (grey) would be neutral.
Specualr maps work from the same shades but white represents reflection or shine and black represents dull or flat...however grey would not necessarily be neutral and would still have some shine or light bounce from it.
The bump and specular maps play off of each other in a little dance. Lots of renders and a good eye will help here.

Much like creating good diffuse maps where you will have lighter and darker tones throughout the body, the same goes for your specular maps. Armpits or skin crease areas won't have a whole lot of specularity happening, but areas like the nose and forehead will have more specular value than the rest of the head (for instance).

I tend to make my specular maps a little more contrasty than my bumps and leaning more towards white than black. But it really depends on the look you are after...everyones tastes are different.

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