How do you personally greet a superior officer outside?

Me in uniform, officer not- salute and greet.
Me not in uniform, officer in uniform- greet
Both not in uniform- greet
I was in the service before fist bumps were even thought of as a greeting. And I don't think you fist bump an officer- unless that officer is extremely cool with it.

First off, what the F is up with that photo...?!?!? ;o)
Two, if in uniform, I look them square in the eye, salute and say "Good morning (afternoon), Sir/Ma'am" If I am in a unit that has a special greeting, like when I was in 3ACR, I will give that instead. If out of uniform, and I recognize them as my commander, I'll salute and give the greeting as well.

A salute and Good morning (and the rank of the person)

I'm old school- higher ups, Good morning or unit motto (Rank), equals- Good morning, subordinates good morning .

Salute with barely audible unit greeting of the day.

If I know the person, I will typically return a salute and salute and greet them by rank and name. If i Do not know them, I will greet them with their rank.

from the front good morning, after noon, good evening, end with sir. from the rear, By your leave Sir

I make it a point to make eye contact, perform a good salute and give the unit greeting. If it's someone I know pretty well I may salute and offer up a "shoot 'em in the face, sir". Or something along those lines.