From personal experience as a Marine recruit in 1966. All of the below applies to while in boot camp.
Anytime you address anyone who isn’t a recruit the first word and the last word out of your mouth is sir.
NEVER us the word, “I.” Use, “Private,” instead.
NEVER use the word, “You,” in any manner that can be possibly construed as meaning any non recruit. You, sounding like ewe, invariably would lead to to some variation of: “Ewe’s a sheep, sheep are for fucking. You trying to fuck me maggot.”
Any reference to a specific Drill Instructer requires the use of the DI’s full title. “Sir, the private requests permission to speak to Senior Drill Instructer Staff Sergeant Whoosit, sir.”
It isn’t a barracks, it’s a squadbay.
The floor is the deck.
Some good phrases you might want to consider a DI using to recruits.
“You’re lower than whale shit and that’s on the bottom of the ocean.”
"Side straddle hops, many, many of them.
“Back to the barn, ladies.”
“Twenty minutes to shit, shower, and shave.” Quite a hoot from the DI’s point of view as up to 100 jammed into the head (never restroom, bathroom, latrine, etc) at once to attend to business.
As mentioned above, “Full Metal Jacket’s,” boot camp segiment is an excellent starting point. R. Lee Ermy, who played the DI was actually a DI for a couple of years.
NEVER, NEVER, NEVER, NEVER use, “Soldier,” to refer to a Marine. It’s Marine.