What is the proper way to address NCOs in different branches?

I grew up in a Navy family. Dad was BM1 and spent his last seven years training recruits at Bainbridge and San Diego NTC. Things may have changed since the late 50s, but he would address anyone E-7 or higher as "Chief". He used the same form of address toward anyone likely to be Navy in civilian clothes, and I never saw a negative response to it. Perhaps sensitivity has changed, but no one seemed to mind the assumption that they were a chief petty officer.

I have worked with all 4 branches at one time or another. When in doubt, just ask the NCO. Grow a set and just ask them. We won't bite. But otherwise, by observation, I learned that the Navy Petty Officers I met went by last name unless they were E-7 and above. Then, it was Chief, Senior Chief, Master Chief, respectively. Marines were always full rank. Staff Sergeant, Gunnery Sergeant, etc. unless they liked you, then you could use gunny or such nicknames (but don't get creative or assume. Make sure they are okay with it first or you will get "sternly" lectured, lol). Army E-5 to E-8 is just Sergeant unless they were 1SG or a SGM/CSM. Then it was First Sergeant or Sergeant Major. Again, if the 1SG liked you, then you could call them Top (again, don't assume, get permission). Every Air Force Sergeant I met went by Sergeant. I sometimes heard Chief used for anyone above Chief Master Sergeant. This is solely from my own experiences but I hope it helps somebody perhaps.

I call him gunney.

I always addressed them by rank. NEVER by sir or ma'am. Those titles are for Officers. The only times an enlisted person is addressed as sir/ma'am is by recruits in basic training.

In the Marine Corps, recruits (because they are in bootbcamp) are required to call every Marine or Sailor Sir/Ma'am. Once a recruit has graduated and earned the title of US Marine, then they are allowed to address a person by their rank.

I usually, for the Navy, ask them what their rank is and how they are addressed. Recently I binge watched JAG. Between that and NCIS, I have a much better idea of what they are called. :)

ONLY THE BOOT ADRESSES THE D.I.AS SIR,AND ONLY IN BOOT CAMP.
REGARDLESS OF THE RANK OF THE NCO HE/SHE ARE ADRESSED AS THEIR RANK,PVT,CPL,SGT,ETC.ETC.ONLY OFFICERS ARE ADRESSED AS SIR/MAAM........
OR AS GUNNY OR SGT/MAJ.FIRST NAMES OFF BASE.....

I was always called "Petty Officer" by my subordinates and the chiefs in my department always referred to my rank before my name when talking to someone about me.
It is my title. The E6's above me were also called "Petty Officer" to me.

We only called petty officers Sir, or Mam in boot camp in the CG. I'm sure that's was the case when you wittnessed those Marine recruits.

Commission Officers these are Sir or Ma'am, Non-commission Officers these are NCO's. There is only three "3" ways to address an NCO, these are - Sergeant / 1st Sergeant and Sergeant Major.

Hello,
I worked with many different branches, if you are uncertain of what to call enlisted ranks in different branches of service, just be polite and respectfully ask how to address their rank. Officers are easy, just refer to them as Sir, or Ma'am!

SFC Port

In Coast Guard and Navy; Chief usually works for E-7,8,9. If you recognize 1 or 2 stars above the anchor you can never go wrong by addressing them as Senior Chief (with 1 star) or Master Chief (with 2 stars) Internally some refer to the E-8 or Senior Chief as "Senior" With that said you would not call the E-9 or Master Chief "Master"

An E-7 in the Marine Corps is addressed as Gunnery Sergeant of "Gunny"
a First Sergeant (has a Diamond between his stripes and rockers) is "First" while a Master Sergeant (E-8 with Crossed Rifles) is addressed as Master Sergeant or 'Top'

a Navy Chief Petty Officer (E-7) is addressed as Chief
a Senior Chief (E-8) as Senior Chief
and a Master Chief (E-9) as Master Chief

The more I was around sailors (most of who jumped out of airplanes) I got to where I recognized and rendered Chief, Senior Chief and Master Chief. Become very close to some of them and they appreciate the effort....the Navy officer insignia's in dress uniform I never did figure out. Also refereed to Gunnery Sergeants in the Corp as Gunny once a rapport was established. Had one bad-ass E-8 we called Master Guns....he had ran the Marine Corps marathon at least a dozen times and was hard as nails but was a very smart guy and very encouraging once ya got to know him. Anywho, you'll pick up on the little nuances as you make your way, particularly when deployed and/or in a combined arms assignment environment. Don't be afraid to ask questions and keep your eye on your Squad Leader or Plt. Sgt. You'll be that guy/gal before you know it. Hooah. Thank you for your service SPC(P) (Join to see) . Best wishes in your career and stay safe.

USCG same as the Navy, Chief, Some E-9 and E9's prefer Senior Chief and Master Chief respectively, but most have told me to just call them Chief. Below E-7, Petty Officer Blank ...

Just address them by their rank. Only the army addresses all NCOs from SGT to MSG as sergeant. In the Marines we learned all the ranks of all branches of the military.

I would initially address them as 'sir' just out of respect for their rank, experience, professional knowledge, acumen, and TIS. If they want you to be a little less formal they will tell you so. Plus you can note how others address them, depending on how well they know them or the professional relationship. A lot of younger people on the outside refer to olders as 'sir' or 'ma'am' for those reasons, not necessarily because the manager or supervisor outranks them.

Personally, if I know the rank, I address them by it and stand as I would for the Army equivalent (GySgt = SFC = Parade Rest etc). If I am unfamiliar with the rank, then I defer to their custom of Sir/Ma'am.

For the USAF, USMC and the Army, "Sergeant" is a good start if you do not know the differences. If you are in a JOINT assignment or assigned to a JOINT base or posting -- LEARN IT.

The Navy and Coast Guard use a mix of their Rating and Rank. (And I am rustly on most of it)
No "Eagle" = "Petty Officer"
"Eagle" (with or without Stars) = "Chief"

Seem to remember when I was stationed on Misawa AFB, all the Air Force personnel called someone of higher rank, regardless of enlisted or officer, sir or ma'am.