Get references and call to check on the work. If possible, go by and visit earlier jobs.
Check with the local Chamber of Commerce or Better Business Bureau for complaints.
Be sure that the contract states exactly what is to be done and how change orders will be handled.
Make as small a downpayment as possible so you wont lose a lot if the contractor fails to complete the job.
Be sure that the contractor has the necessary permits, licenses, and insurance.
Be sure that the contract states when the work will be completed and what recourse you have if it isnt. Also remember that in many instances you can cancel a contract within three business days of signing it.
Ask if the contractors workers will do the entire job or whether subcontractors will do parts.
Get the contractor to indemnify you if work does not meet local building codes or regulations.
Be sure that the contract specifies the contractor will clean up after the job and be responsible for any damage.
Guarantee that materials used meet your specifications.
Dont make the final payment until youre satisfied with the work.