I've over-packed for weekend trips and under-packed for three-week ones, so this list exists mostly to keep my past self honest. It's built for general US travel — road trips, city breaks, national parks — and adjusts easily for climate and length of trip.

The non-negotiables

A reliable daypack, a portable charger, a printed copy of your key confirmations (in case your phone dies at the worst possible moment), and one "nice enough" outfit that works for an unplanned dinner out. Everything else is adjustable; these four rarely are.

• Layers, not a single heavy jacket: A packable rain shell plus a mid layer beats one bulky coat for almost any US climate.
• A real water bottle: Refillable stations are everywhere now, and it saves real money over a week-long trip.
• Offline maps, downloaded before you go: Cell service disappears in more places than you'd expect — national parks, mountain roads, rural stretches.
• A basic first-aid kit: Blister pads and pain relievers specifically; you don't need the full kit for most trips.
• One dedicated "documents" pouch: ID, cards, printed confirmations, all in one place you check obsessively.

What people over-pack

Shoes, mostly. Two pairs covers almost any trip: one comfortable walking shoe and one you wouldn't mind wearing to dinner. Beyond that, most people pack for a version of the trip where they change outfits far more than they actually will.

Lay everything out before you pack it. You'll always find at least one thing you don't need.

Trip-specific additions

National parks: bug spray, a headlamp, and shoes you've already broken in. City breaks: a cross-body bag you can keep in front of you on transit. Road trips: a phone mount, an aux cable or adapter, and snacks that won't melt in a hot car.