Get a Written Contract.
Be sure you read and understand everything in your contract before you sign. For large projects, you may want to seek legal advice.
Contract should at least include:
Price, including sales tax.
Payment terms, such as paying as work is completed and completion date.
, if applicable.
The specific work to be performed.
A list of materials, major suppliers, and subcontractors to be used.
Warranties and processes for changing orders.