For me.
Before I enlisted in the USMC (Pre 1990):
Slouching posture.
No eye contact what so ever.
Shuffled feet constantly when “standing still”.
Walked like I was trying to launch myself off the earth with each step.
Wore whatever was closest to my face when I rolled out of bed.
Spoke unclearly and used Umm and dude as conjunctions.
Tended to wait until told to do something before taking any action.
After I enlisted in the USMC (Post 1990)
Stood tall shoulders back, eyes up.
Look people in the eye when speaking to them and make eye contact as much as possible with passers by.
Stand still with feet slightly apart and hands comfortably behind my back when in line or other situations where standing around is required.
Walk smoothly and in line (not time) with the person(s) I am walking with.
Attempt to appropriately match my clothing to the activities of the day. Also attempt to keep those items clean, neat and ironed.
Keep conversation appropriate to the context. Dude and man may be ok with the buddies at the bar but never in the workplace. Even amongst friends.
Take the initiative when I deem it appropriate. Follow directions when appropriate.
All in all a total transformation from young suburban punk to military proper man. I would hazard a guess that people pick up on these and other overt behaviors and recognize military training even though I may not always appear to be military from my general style. (i.e. Long hair, unusual clothing styles)