1. Get different quotes. All contractors have their own fee.
2. Make sure they are licensed in your state.
3. Check their references.
4. Do not pay everything in advance. Usually is 10 percent depending on the state.
5. Do they have insurance. What kind? Ask for a certificate and verify it.
6. Check to see if they have a record with the Department of Consumers Affairs?
7. Understand and read carefully the contract you are signing.
8. Drive around the work they have done to check in detail and talk to prior clients.