1. Don't overbuy in the first place. Imagine this: it's move-out day. You're finally clearing out the space under your kid's bed. It's apparent no one in their right mind—with the exception, of course, being you—has explored that chaos since August. Amidst candy wrappers, beer bottles, and your son's trusty pet mouse who lives under the heater, you see a layer of dust obscuring the once-new coffee maker you thought would make a "homey" addition to his room. After one use, it's caked in coffee residue, mold, and dust. That's not to say some people wouldn't treat their coffee pot—a sacrosanct tool for some—with better care. But know your kid. Don't needlessly spend money on items that end up locked away for months, often only to be thrown out or given away anyway.
Hack: Budget your move-in day spending with an exact figure or set a $100 range. Create your budget solely around the essentials (pillow, blanket, hamper, mirror, hangers, etc.). Don't create a budget mid-shopping. You can always think of uses for products in the moment, but once you leave the store, it's hard to justify why your kid needed a disco lamp. This prevents waste on move-out day, avoids clutter, and saves you money.