1. Look before you touch anything
Note what you're seeing, stop further damage if it's safe to do so, and gather whatever history you have on the roof.
2. Look at the whole assembly
Deck condition, underlayment, flashing, ventilation, fasteners, roof shape, drainage, and wind-code requirements all affect how the roof performs, not just the surface material.
3. Put the scope in writing
Preparation, protection, materials, access, permits, testing, cleanup, and change-order terms should all be spelled out.
4. Weigh more than the total
Compare how each provider explains their approach and where the boundaries of the job sit.
5. Walk the finished job
Confirm testing, cleanup, paperwork, warranties, and what maintenance is left to you.