Here are some I recall from modern times:
The only real formation in combat is skirmish line. Localize the contact, build the firing line, establish fire superiority, and get moving.
Violence of action will carry the day. Immediate action drills must be rehearsed relentlessly to ensure unity of effort and break the inclination to go prone.
The ambush mentality must be adopted and applied in every situation it can be.
Casualties wait until the gunfight is finished and the objective is consolidated on. It really sucks to get kicked out of a house/compound because you were tending to other things when the bad guys decided they wanted it back.
When it’s time, use HIS kit, not yours, and remember you’re not an MD, nor is a bunch of pissing and moaning going to help; get him breathing, stop his bleeding, wrap it up and get him out of there.
You never have enough leaders in combat; span is limited to arm’s length while bullets are flying. A platoon with a platoon commander, platoon sergeant, guide, three squad leaders, and nine fireteam leaders is still not enough.
The T/O is in threes for a reason (division of three regiments of three battalions of three companies of three platoons of three squads of three fireteams). This works out perfectly for base of fire, assault element, and reserve, and when things go to shit you must adapt on the fly to meet the threat but you must also not leave that framework, and don’t ever get caught “with all three legs in the air.”
You must keep a reserve, as large a percentage of your overall force as the tactical situation will allow, because once there is contact commanders only control the units that are not engaged.
”Don’t reinforce failure” is a tenet of maneuver warfare, but that doesn’t mean you can’t commit your reserve to buy your assault element room to maneuver, even if it’s to pull back. Too many leaders want to push a second axis of advance and now you’ve got two (or worse, three!) separate fights going on.
The bad guys are going to show up where you didn’t want them to, so fire plans/schemes of maneuver must show the alternate, and especially the supplemental positions/responsibilities.
Employ machine guns in pairs.
Unit boundaries must be unambiguous and adhered to.
Comms will go to shit, so don’t forget the good old Signal Plan using pop-ups and smoke, and review it every single day.
Every single man must know the Signal Plan, at least cease fire and need help ASAP, and have the means to carry it out.
It’s okay to tell higher headquarters to clear the net while there’s shooting going on.
Water, batteries, ammo, and cigarettes are all you really need to survive 😉