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

Call him or her Gunny. Short for Gunnery Sergeant. They would appreciate that.

When I was in the AF I only ever referred to someone of equal or lower rank by their first name if I knew them well and worked with them regularly. E-1 to E-4 were Airman. E-5 to E-8 Sergeant unless a First Sergeant E-7 to E-8. Then it was was First Sergeant, Top, or Shirt. E-9 was always Chief. Never referred to an officer by first name on or off-duty.

If the rrecruit is taking to anyone while in boot camp, I can understand it. But with that being said, rank should also be expected to be addressed appropriately. But just don't confuse recruits with those that have already graduated.

Recruits don't rate to call anyone anything other than Sir or Ma'am. Once you graduate boot camp and earn the title of US Marine, you call enlisted by their rank. If you can't distinguish their rank due to uniform, eyesight, etc, err on the side of caution and call them sir. Especially in woodlands, it's pretty hard to tell the difference between a SSgt (E-6) and a GySgt (E-7)

Marines call their Drill Instructors sir or ma'am. But out in the fleet we call them corporal, sergeant, gunny, top/Master sergeant and Master guns or Master gunny.

called my DS "Sir' first time I met him, or should I say encountered him. anyone under the rank of E5 in my unit was either by their name or some nice derogatory remark. 1st Sgt was TOP (unless you were visiting his office) all E5 and above were Sarge. most E6 were Staff, and again E7 and above were Sarge. But it really changed dramatically when your in the field.

look at all these sirs and ma'ams!! lol

Officers are Sir or Mam . NC0s by their rank. Chief Warrant Officers are Sir or chief or chief warrant officer

I can't believe they let you be an E-4 .....seriously.

With respect like you would want anyone to give to you. If, respectful I can only assume he or she can explain respectfully address them.