When hiring a contractor in California, there are several important facts and regulations you should be aware of to ensure a smooth and legal engagement. Here are some key points to consider:

1. Licensing Requirements: In California, contractors working on projects that exceed $500 in labor and materials must be licensed by the California State License Board (CSLB). Verify the contractor's license status and history online through the CSLB website.

2. Workers' Compensation Insurance: Contractors should have workers' compensation insurance for their employees. This protects you from liability if a worker is injured while on your property.

3. Contractor Bonds: California requires contractors to have a contractor's bond of $15,000. This bond is in place to protect consumers in case the contractor fails to complete a job as agreed or commits a violation of the Contractors State License Law.

4. Written Contracts: For home improvement projects over $500, California law requires a written contract. The contract should detail the scope of work, materials to be used, costs, payment schedules, and timelines.

5. Down Payment: California law limits the down payment that contractors can ask for at the start of a home improvement project to 10% of the total contract price or $1,000, whichever is less.

6. Mechanic's Liens: Understand the potential for mechanic's liens, which can be placed on your property if the contractor does not pay for materials or labor. You can protect yourself by requiring lien releases from subcontractors and suppliers.

7. Home Improvement Salespersons (HIS): If someone other than the contractor who will be performing the work negotiates your contract, they must be registered as a Home Improvement Salesperson with the CSLB.

8. Building Permits: Ensure that all necessary building permits are obtained before work begins. It's often the contractor's responsibility to obtain these permits, but the homeowner is ultimately responsible for ensuring that all work is permitted and complies with local building codes.

9. Right to Cancel: For home solicitation contracts, California law generally gives you the right to cancel the contract within three business days without any penalty.

10. Dispute Resolution: Familiarize yourself with the dispute resolution options available, including the CSLB's complaint process and options for mediation or arbitration in case of disputes.

11. Energy Efficiency: For certain types of work, especially those that involve electrical or plumbing systems, contractors must comply with California's energy efficiency standards, which are some of the strictest in the nation.

Before hiring a contractor, it's also advisable to get multiple bids, check references, and review the contractor's previous work when possible. This due diligence can help ensure a successful project and protect your interests.