For "genealogy" start with talking to oldest relatives or children living for their memories about him. Start a paper trail. Order his death certificate, depending on where he died and when it might have his parents names if known by informant. Did he have a Social Security Number? You can order a copy of his application that asks for parents names, including mother's maiden and places of birth, again if known by him when he filed.
As for Military service records look at the NARA website for information about Service records. www.archives.gov Was an obituary published? Some family include military service information. Did he have Military Honors at his funeral? If so contact the local VA, Military Veteran's orginzations who provide them.
Usually local state and counties have lists or memorials for those who served, some are online as is Missouri's or you have to contact a State Archives Dept. Where was he living when he served? Here is a website for State records transcribed and uploaded by volunteers for online use by reseachers. http://usgenweb.org/http://usgenweb.org/
The LDS Family History Center has records, books and microfilm rentals usage.