I would like to contact someone from my past (20 years ago) at his work place so as to not disrupt his family life. How do I find out a phone number for him?
Personal email, home address/phone and personal cell are not options as I may disrupt his family. Any ideas? I do know what city he lives in. I believe he may be working for the army.

You hire an investigator but investigators are more and more careful about the info they provide, particularly if they don't know the reason the info is "needed." If you know where he lives (which is easy to obtain) then follow him to his place of employment.

I'm an investigator. I would not locate anyone under these circumsances.

With so many social media sites out there today, have you tried looking on Facebook, class reunion sites like classmates.com (if you knew schools he had attended), whitepages.com for an address listing, Google plus, mylife.com or LinkedIn? On LinkedIn, you may even be able to see a place of employment, if he listed it.

If you are just looking to catch up with an old friend, these sites may be helpful and unobtrusive if you are unsure about disrupting his current life. If someone does not want to found or contacted, they would not make profiles public.

You may not have the time to sift through social media or maybe he has no profiles at all. In this case, you may want to look into hiring a Private Investigator. There are many, many Private Investigators out there and numerous websites that say they can get all sorts of information. Being in the search industry for a few years, I have found that Searchbug.com has reliable investigators, good guarantee policies and have positive results for searches. You might want to take a look at the searches they have to see if any suit your needs if you can’t locate anything online. Here is a link to a place of employment locate if it helps you. SearchBug - Place Of Employment Search (POE)