You cannot serve anyone. You need to get someone else to serve on your behalf. If he is represented by counsel, then the RFO is served on his attorney. The RFO can be served by U.S. Mail.
Given that temporary orders have issued, I am assuming that both you and your ex showed up at court the day these orders were requested. The reason this assumption is necessary is because I am assuming that both of you have made a general appearance in this matter. This is a legal technical term that gives the court indication about whether the court has jurisdiction over the parties and whether the parties have notice and have had the opportunity to review and respond to the initiating Complaint and/or Petition.
Once general appearances have been made by both parties, the Request for Order can be served via mail by someone OTHER THAN YOU who is not a party to the action and who is over the age of 18. Since the other party is represented by counsel, then it is appropriate to serve the RFO on their attorney. This can also be done by mail by a third party over the age of 18. Remember to have this person sign a Proof of Service form showing the court when and where service was effectuated.
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I agree with my colleagues. You cannot serve the RFO by yourself, and need a third party who is over 18 to serve it. As the other party has an attorney of record, you will need to serve that party's attorney. Service can be made either personally or via u.s. mail. The person effectuating service must serve the RFO no later than 16 court days before the hearing for service to be timely. If they serve it for you by mail, ensure that they add 5 calendar days if it is mailed to/from California, or 10 calendar days if it is mailed to/from a location outside of California (add 20 days if international). Ensure that the person serving fills out the appropriate "proof of service" form (e.g "proof of service by mail" or "proof of service by personal service"). I would also recommend filing the proof of service with the court prior to the hearing to prevent the other side from claiming they were not served timely.
Please be advised that the answer above is a very general answer, which may not apply to the fact-specific circumstances of your case. I suggest, advise and encourage you to speak to an attorney right away regarding your situation.