What are the best techniques for sanding wood filler to achieve a smooth finish when using sandable wood filler?

To achieve a smooth finish when sanding wood filler, start with a coarse grit sandpaper to remove excess filler, then switch to a finer grit sandpaper for a smooth finish. Sand in the direction of the wood grain and use a sanding block for even pressure. Finish by wiping the surface clean before applying any stain or finish.