Looking at the entire U.S. government, military and intelligence agencies are the most circumspect and make the smallest amount of information publicly available. This is partly due to the nature of military and intelligence activities, but it is also part of the institutional culture to tightly control information and its dissemination. In addition, service members face severe penalties for unauthorized release of information.
Military agencies and units have public affairs officers who may be the first point of contact. It is helpful to have an understanding of where the agency fits in the military hierarchy.