Sandpaper isn't cheap. Here's a way to prolong its use as well as recycle your worn out shoes.
Sandpaper can get gunked up after just a few passes of wood, rendering it ineffective. Serious woodworkers invest in abrasive cleaning sticks to clean dirty belt, disc and orbit sanders. But, if you don't have one handy, you can use the sole of an old shoe to clean your sanders.
With the sander running, gently rub your shoe's rubber sole against the sandpaper in a sweeping motion. One or two passes will have your sandpaper looking almost new again. Check out the video to see the trick in action.
How to clean sandpaper using an old shoe [Izzy Swan (YouTube)]