What constitutes being "old school" in the military?

I still have a pair of Khakis in my closet - Waiting for the Army to come to Its Senses and bring them back (best damned uniform a Paratrooper ever wore).

Real easy...it's not about what old ass vehicle you rode in(in my case M880)or what model M-16 you used. It's about your mindset. You are dedicated to the service, without it you are NOTHING! Without you it is NOTHING! Your weapon IS your priority! When you are wet, cold and filthy...it is dry, warm and clean! When you have ANY down time, the first thing is it's care...before you eat, sleep or shit. Hard training makes you harder, therefor it is not only welcome, it is pursued. Always strive to be better than you leadership, therefor your leadership has no choice but to be the best. Nothing is more important than your squad, which is more important than your platoon, which is more important than your company, which is more important than your battalion, which is more important than your regiment. AND YOUR REGIMENT IS EVERYTHING! That, ladies and gentlemen, is what being "Old School" is.

I road around in a ¼ ton in my OD green fatigues.

No it would be the warfieghters. The ones that deployed every other year. Before that it was the cold war soldiers that trained for old school combat. Before then it was the Vietnam vets. 15 years is a rough generation in the military.

Not only know what a gamma goat was, but actually had to ride in the damned things (was bounced out once going down a FU trail!)

Your uniform was just one color (OD Green), goes with "Breaking Starch" (Class B Kacki's as well)

Actually hated giving up C-Rations for MRE's (Brown 1st gen)

In a Steel Pot of warm water, you could shave, brush your teeth, bathe, and if you were good (read experience) have enough water left for a cup of coffee

You found a set of M16 hand guards that had Mattel stamped on the inside (me, only once)

As a patrol leader, you actually also carried a radio

You know what Tigerstrip is

You also know what a LLRP is

When you don't complain about doing things that make absolutely no sense because that's just how the Army is

NO REGRETS

I have done nearly 90% of what Major Petrarca listed above. Plus, I've eaten C rations, wore OD fatigues with white lettering on blue name tapes with full color command patches. Carried LBE back packs (both medium and large). Drove 1/4 ton M-151s, duece and a halfs, AT fork lifts, and the staff car for my CO. Shaved, bathed, but never cooked out of my M-1 helmet! Cooked and ate from a mess kit (he forgot that one). Slept in shelter halfs put together, on the ground, those hard as rocks cots and wore the USAF all purpose white PT snorts. Life before MREs was really interesting.

It's gonna depend a lot on your generation. For us (BASD 22AUG66) old school was someone who originally qualified on an M1 Garand, had worn lace-up leggings, brown boots, HBT fatigues, and drove an M-38 quarter-ton. They also wore a World War Two Victory Medal ribbon on their class-A uniform.

Know what a p-38 is for, wore fatigues, issued white undies, wore a pile hat in the winter,took a pro pay test.