Here are some helpful documents and links which may be of interest:

Documents:
» California Employees Withholding Allowance Certificate
» US Form W-4 - Employee's Withholding Allowance Certificate
» US Form W-9 - Request for Taxpayer Identification Number and Certification
» US Form I-9 - Employment Eligibility Verification

Useful Links:
» California Employment Development Department
» California Department of Fair Housing and Employment
» California Franchise Tax Board
» US Department of Labor
» US OSHA
» US Internal Revenue Service