How do I serve a parent if I don't know his address or whereabouts?

In some types of cases, you can provide legal notice to the other party by publication in the newspaper, if you are unable to locate them.  You must sign an affidavit stating that you have used due diligence to try to locate the other party and have been unable to locate them.  Some of the things that constitute due diligence include conducting an internet search, checking utility and DMV records, and checking with the Post Office for a change of address.  Some people choose to spend a small fee to have a private investigator do their due diligence for them.  You will need to provide the party's last known address to the court.  Once the legal notice runs in the newspaper once a week for four weeks, you should be able to proceed with your case.  It may make sense to hire a lawyer to take care for this for you, since we are accustomed to the procedures of legal notice. This answer is given in accordance with the laws of Virginia and may not be applicable in any other state.  It should not be construed as legal advice, as that would require a more thorough analysis of all of the facts involved in a specific case.  If you need further information or assistance, please feel free to contact my office for a consultation. Case results depend upon a variety of factors unique to each case. Case results do not guarantee or predict a similar result in any future case.