Run by the National Archives, the National Personnel Records Center is the repository for all military personnel and medical records ("Official Military Personnel File", or OMPF) of discharged or deceased veterans.
Information available includes: duty stations, training, awards, disciplinary records, evaluations, insurance, discharge information, etc.
To obtain the records, the servicemember or next of kin can fill out the SF 180, Request Pertaining to Military Records, and send it to one of the addresses indicated on the form, depending upon the servicemember's branch and years of service.
Because most military records are protected by the Privacy Act, attorneys cannot subpoena them without a judge's signature. Obtain a court order for the records, which includes a description of the records sought, and the following information about the servicemember: name, SSN, date of birth, branch of service, and dates of service. If medical records are sought, include dates and places of treatment.
Send a copy of the court order to:
National Personnel Records Center, (NARA)
(Military Personnel Records)
9700 Page Avenue
St. Louis, MO 63132-5100
Records for servicemembers still on active duty are obtainable in a similar fashion - consult the address blocks on the SF 180 to determine where to send that form, or a court order.
Legal Demands for Records/Information (PRC 1864.107D). NPRC Memo on obtaining records via court order.