Get everything in a written contract. Scope, materials, start and finish dates, payment schedule and how changes are handled. If it isn’t written down, it isn’t agreed.
Tie payments to milestones. Pay as work is completed (demo, rough-in, drywall, finish), not mostly up front.
Ask who pulls the permits. For work that needs permits, the contractor should get them. Skipping permits can cause problems when you sell or insure your home.
Check references and past work. Ask for 2–3 recent clients you can call, and photos of similar projects.