Are you covered?
This is a question with no wiggle room. Under so circumstances should you work with an individual or company that is not licensed and bonded. That means requesting–and verifying–proof that he or she is currently state licensed, paying employees legally and carrying workers’ compensation, property damage and liability insurance.
What clubs do you belong to?
If your prospective contractor has a list of clubs and associations they belong to, it’s always a good sign. Usually, members are encouraged to attend continuing education program courses, and they often receive professional designations such as Certified Graduate Builder (CGB).
What is the estimate?
Along with the other questions you want to ask during the process of hiring a contractor , you should request an itemized estimate from each. Be sure to look over the information thoroughly, paying particular attention to those that seem too high as well as too low. Estimates that fall in the shallow end of the pool can be a red flag for a hasty job that won’t leave you with a quality product; those on the high end might have artificially inflated prices.
Can I have a copy of the schedule?
You need to know exactly how long that kitchen renovation  is going to take. Before you hire a contractor, you should ask them to provide you with a fixed start date and a completion date–including any cleanup duties. These dates should be included in the formal written agreement, along with a timetable of the work that’ll be done and a material list of everything that’ll be needed.
What is the payment schedule?
Most professional builders work on a pay-as-you-go basis, receiving partial payments throughout the process. The payments for new construction, also called draws, typically are scheduled as a certain percentage of the total cost when specific stages of construction are completed. Avoid any contractor who wants full payment before starting the job.
In addition to your references, can I have a list of previous customers?
It’s one thing to talk to a list of people the contractor has prepared for your call; it’s another thing to cold call prior customers from whom you’re more likely to get an honest assessment.
Can I see some of your projects?
Good builders are proud of their work and enjoy showing it to potential clients. Ask to see photographs of complete projects, and choose someone whose work looks similar to the job you’re planning.
How do you schedule call backs?
You want to know what to expect and how to best contact the contractor if, for any reason, they need to come back and fix or redo a job. Go with the person that has a concrete plan for these types of issues.
How to Set Your Home Improvement Plan 
Hiring a Contractor: When to Know When You Need One 
How to Get Along With Contractors