Try hiding bits of your model so you can see exactly what's going on underneath the surface.
Then it's Smooth and Reduce ad nauseum. turn the strength of the smooth up and the reduce to mid way.
Sometimes you have to go over it many times before it comes out.
As for prevention, keep your strengths relatively low in normal use and use multiple passes to get stuff done. If you're going to twist or rotate any parts of your model make sure that you use a mask with a gradual falloff as opposed to a sharp edge.
I'm no expert, but this is what has worked for me so far.