Your home is your most important investment. Get the maximum return out of your investment by choosing the most optimal contractor for your needs.

State Contractor Licensing (they must provide the number if licensed) *:

Each type of contracting requires a separate specialty license from the State of California.  In addition, if the work you are considering is valued at $500.00 or more, a valid California Contractor’s license is required.

Insurance (ask to see their certificates): 

Make sure the contractor has both Workers Compensation and General Liability Insurance.
This is important for you because, if a worker is injured while working on your property and the contractor does not have insurance, the homeowner is the one who will be liable.  Ask to see certificates proving insurance coverage.

Business Longevity
Check how long the contractor is in business. Avoid if possible the new and fly by night operators.

Stability and Permanence:
Does the contractor have a physical office address? Is that reasonably close to your home?

Reference Check (yes, you should check references)
Always ask for references and check them

Experience
Perhaps most important, see the portfolio to make sure you like them