They say that beauty is only skin deep. That's particularly true for wood because it is the surface of wood that you see. Nothing can effect that surface more than sanding.
A hacksaw blade mounted to a piece of wood makes a great sandpaper cutter.
Fold your sandpaper into thirds. Use one side of the folded paper first, then the reverse side and finally refold the paper to expose the third side.
Always sand in the direction of the wood's grain. Sanding across the grain can leave scratches, which become even more apparent when the wood is stained.