Substituted service is ONLY allowed when service is NOT POSSIBLE. Service in this manner STILL needs to be handled by a third party, Sheriff's Officer, or Process Service, and documents need to be prepared in the same manner as they would for personal service. When using this method of service the following forms should be used:
For Substituted Service:
The server tries to personally serve the papers on the other party a number of times (usually 3 or more), but cannot find the party at home (or work, if that is the address the server has). The server must try different days of the week and different times of the day, at times when the other person is likely to be home (or at work if serving him or her there).
If the server is unable to find the person to be served, he or she can leave the papers with someone at the other party’s address, so long as the service takes place between the hours of 8:00 A.M. and 8:00 P.M., and the person receiving the papers is at least 18 years of age. (CCCP §1011(b)), (Sweeting v. Murat (App. 2 Dist. 2013) 164 Cal.Rptr.3d 383, 221 Cal.App.4th 507).
If there is no one over the age of 18 home at the time of service, the notice or papers can be served by mail (CCCP §1011(b)) (see information in "Service by Mail" tab).
Unlike the requirements for the Service of Summons, the server DOES NOT need to mail a copy of the papers to the other party at the address where the papers were left. (CCCP §415.20(b)).
The server must then fill out a Proof of Service, detailing when, where, and how the papers were served. The server has to make sure to write the name of the person he or she left the papers with (or a detailed physical description). The server signs the Proof of Service and returns it to you to file at the court.
If the party's residence address is unknown, service may be made by delivering the notice or papers to the clerk of the court (CCCP §1011(b)(3)).
The notice or papers delivered to the clerk must be:
"Service is being made under Code of Civil Procedure §1011(b) on a party whose residence address is unknown, [Name of party whose residence address is unknown] and [Case name and number]."
Only a summons may be served on a party by publication. The publication must be in a named newspaper published in 
the state that is most likely to give actual notice to the party to be served. See CCP §415.50, §415.95, §417.10(b), and the Research Guide for Service of Summons and Complaint.
San Diego Superior Court has a list of approved newspapers for publication of legal notices.
Service in this manner STILL needs to be handled by a third party, Sheriff's Officer, or Process Service, and documents must be prepared in 
the same manner as they would for personal service. When using this method of service the following forms should be used:
Substituted Service on an Attorney
If the party being served is represented by an attorney, service on the attorney may also be made by leaving the notice or other papers in an envelope or package clearly labeled with the name of the attorney being served.
The envelope or package can be left with an office receptionist or person in charge of the office. If there is not a person in the office that can receive the papers, AND it is between 9:00 A.M. and 5:00 P.M., service can be made by leaving the envelope or package in an obvious place in the office (CCCP §1011(a)).
Additionally, a shared receptionist in a suite of offices shared by several lawyers has been determined to be a person on whom service can be made (National Advertising Co. v. City of Rohnert Park), even if the receptionist was not authorized by the attorney to receive service. There is also a presumption that papers placed in mail slots or compartments in outer doors of a business office will be received by the addressee.