So, most representations suggest that Superman has indestructible hair. It makes some sense (though not a huge amount), though it depends on how Superman's powers are supposed to work.
One thing I wonder, though, is what the texture must be like. I mean, I'm sure the hair on his head is relatively normal, but depending on the artist, Superman's often been shown to be pretty hirsute. Body hair, at least in my limited experience, is generally fairly coarse; would body hair of steel in turn be like steel wool? If Clark Kent's showering, does he wear holes in the washcloth with his indestructible man-fur?
If I were to guess, I'd suspect that his hair is the same texture as human hair, but much stronger, but what does that mean for his plumbing? I imagine the super-mullet was hell on his drains.