If you have polish on, remove it. If you are wearing polish on your nails, this can be a trick. Nail Techs are taught to put your chosen polish remover pads between your knuckles and scrub the polish off that way, but I prefer to put on some rubber gloves and do it. Also, you can dampen 10 pads and lay one on each toe for a minute, then go back and remove the polish much easier.
If your feet are really dirty, stand in your bathtub and wash them off a little first, just so your pedicure bath can stay luxurious and not get nasty too quickly.