This issue's trick is from Chris Bauer at Bauer Hardwood Flooring in Sacramento, Calif.:
Here's another dollar store delight: cheap, effective disposable shoe cleaning doormats for rainy and muddy job conditions! At least here in California, most Dollar Tree and 99¢ Stores carry five-packs of puppy trainer pads to absorb pet urine while housebreaking a dog. The XL version are doormat-size pads that are excellent at absorbing moisture and wiping dirty, wet shoes off when working at most standard job sites with lawns. You can double-layer or triple-layer them just outside the entry points of your work area and rotate them to a clean pad as they get too dirty. They are also good to use during the final floor sanding even when it's not wet conditions, or as a tool mat to protect a prefinished floor. I used to put terrycloth towels at doorways for the same purpose, but the towels are smaller and more expensive than the puppy pads. (To see other dollar store tips from Bauer, go here.)