Hopefully you're talking about corners. The easy fix to this is to put a little paper around the bit that sticks into the corner, so it doesn't slip out.
If it's "centers" then the advice is a little less appealing. All you can do is tighten the cube up a bit, and work on your turning style so it's not as rough. I find that the smoother my turning style the faster I am at skewb anyway.