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Depending on how long they have been living there, the proper notice can be 30 days (less then 12 months) or 60 days (more than 12 months).
If they are violating the terms of the lease agreement (using the pad for washing, etc.) a "3 day notice to cure or quit" can be issued. (A good trick is to issue both the 3 day and the 30 day (or 60 day) at the same time - what this does is it gives the tenant 3 days notice to stop violating the lease terms (so they must stop breaking the lease within 3 days or face immediate eviction), but it also terminates the lease within the 30 days (or 60 days)).
The California Attorney General probably has the best guide to Landlord/Tenant information in California: http://www.dca.ca.gov/publications/landlordbook/index.shtml
If these individuals fail to leave, you can use the unlawful detainer ("eviction") process to force them to leave, the California Courts have an excellent website to assist you (complete with all necessary forms): http://www.courts.ca.gov/selfhelp-eviction.htm