Go out and wear them while walking on cement or rough blacktop. Grind the shoe into the ground, make sure the sole gets scratched up.
This won't help much if you're walking on ice, but should be sufficient to handle most normal walking surfaces.
I actually have this issue with leather bottomed dance shoes quite often. They're so slick when I first get them that my lead can push me across the floor; it's hard for me to stop myself from sliding.
If they are leather on the bottom, the quick fix is a bit of water, it'll temporarily stop them completely from sliding.