'Officers' are members of Starfleet or the DFA who have voluntarily completed four years in their respective academies.
Non Commissioned Officers are those that do not take four years in the academy, instead opting for more direct training that lasts for about one year.
Warrant Officers are NCO's that have recieved enough training to achieve a commissioned rank.
The game standard is that of Her Majesty's Navy. It is relatively simple and nearly reflects that of Star Trek: The Next Generation. It implies:
Flag officers: All flag officers are called 'Admiral,' in direct address, regardless of grade. A Commodore is called 'Commodore.'
Captain or Commanding Officer: The Captain is called 'Captain' in direct address, regardless of grade. Some smaller ships have captains which are not Captains (O-6); however, while on their vessels they are addressed as 'Captain.'
Officer: Any other officer is called either by rank or 'Mister.' Note below on truncation of Naval O-4/O-2 and the marine ranks.
Mister or Miss: 'Mister' is an appropriate form of address both for superiors and subordinates. You may call a superior up to the rank of O-4 'Mister' without giving offense. Courtesy dictates calling the XO 'Commander,' if he is an O-4 or O-5.
Flag Officers (O-7/F-1 through O-11/F-5) Commodores (O-7) are addressed as 'Commodore.' All admirals, regardless of their rank, are addressed as 'Admiral,' not 'Branch Admiral,' 'Senior Admiral,' 'Fleet Admiral,' etc.
Senior Naval Officers (O-4 to O-6) Captains and full commanders are addressed as 'Captain' and 'Commander,' respectively. A lieutenant commander is addressed as 'Commander.' At his pleasure, an O-6 and above may address an O-4 (LCDR) as 'Mister,' but he should know that he is giving offense to the officer, by implying that he is a junior officer.
Junior Naval Officers (O-1 to O-3)
Junior officers are addressed either by their ranks or as 'Mister Smith.' They should refer to each other in this manner. At the pleasure of senior officers, female junior officers may be called 'Ms. Smith.'
Should we encounter any cadets, midshipmen, or officer-candidates, they are addressed as 'Mr./Ms. Smith.'
Limited Duty Officers
Warrant Officers are properly addressed as 'Mr. McGuinn,' etc. They are not to be called 'Chief' in the NAVY. They very definitely rate 'Sir,' from enlisted crewman and NCOs.
Marines are addressed by their rank. They are not called 'Mister.' Obviously, in direct address, LMaj and LCol's are called 'Major' and 'Colonel' respectively.
NCOs and Enlisted crewmen
NCOs are addressed solely by their rank. All chief petty officers regardless of grade are called 'Chief.' Likewise, all 'Corporals' and 'Sergeants' are called such, regardless of their grades. A 'Sergeant-Major' is called such, unless an officer wants his teeth knocked out. Enlisted crewman are typically called by last names, *without* 'Mister' attached or as 'Yeoman.'
Ways to report
There are two 'accepted' ways to report:
"Smith, John, *Master Chief Petty Officer* reporting for orders, Sir."
(preferred by hard core old liners and NCOs AND marines.)
"Ensign John Smith reporting for orders, Sir."
(preferred by most junior officers.)