1. Fundamentals

Regardless of which branch of service you belong to, or whose guidance you follow, there are a few fundamentals that are universal.

First and foremost learn to identify the ranks of not only your branch but everyone else. The adage "when in doubt whip it out" regarding the saluting of any rank that your unsure of is lame, first all you don't salute enlisted ranks, and aside from naval officers all of the other branches are the same.
Next and closely tied to the first, learn how and when to salute.
Then learn and polish the position of attention and stationary drill movements.
Lastly learn how to march; it's the military way of walking.

Beyond the ranks I would like to eventually detail cultural aspects of the Army, Air Force, and Navy.