Start with the room that bugs you most — momentum beats logic. Clear a staging zone in the garage or driveway first so you always have somewhere to put things.
Use four piles: keep, donate, sell, haul. Anything you touch twice without deciding goes to haul. Set a timer per room; 45 minutes is enough to make visible progress without burning out.
Book your pickup before you start. A scheduled truck is the deadline that keeps the 'maybe' pile from moving back inside.