hey guys and gals, i thought we could start a thread with useful hints and tips. there are so many things you can do in this game that it's hard to keep track of them all.
like for example...

How to assign fire teams

as team leader you see your team members in the bottom left of the screen. it can be hard to keep track of them all. by hitting the f-keys you can select team members. the team leader is F1 and so on. say you have a squad of five. team leader, medic (f2), automatic rifleman (f3), rifleman (f4), automatic rifleman (f5), rifleman (f6). when you select F3 and F4 - your AR and R, you'll get a command menu in the upper left of your screen. scroll down to Team, hit enter and scroll down the new menu. assign F3 and F4 to Team Red. assign F5 and F6 to team blue. since you are the squad leader you won't be in a fire team, as you need to run around on your own. and you want your medic to be in a secure position and not on a flank.

this allows you to yell orders at your fire teams, "red team: left side, blue team: right side!", but it also helps your teams determining who is who on STHUD, since Team red will show up as red dots and Team Blue will show up as, you guessed it, blue dots.</p>

In night missions crank the gamma up so you can see.

Controls

Arma has a robust set of custom options for defining input such as double tapping or 2 digit "chording" (when holding down two keys at the same time trigger a completely different input). For example i have the default WASD setup for movement but if i hold "A+D" at the same time i'll crouch, "W+S" goes prone, double tapping "W" will stand up, "Q+E" switches my secondary/primary weapons.

Stick something with a texture to it on your "V" key. The idea is to make it the "V" key a tactile reference point if you're someone like me and has a habit of looking down to see which key my thumb is on. This makes the row of the "Z - M" keys more usable for me personally.

The squad control system can get cumbersome if you want to get into some complex commands, so i'd recommend a voice recognition controller. This VAC seems to be a popular one and has a 14 day trial.

Gameplay

When playing as a commander (high command) you stay at the HQ and play from the map screen like an RTS game. Rather than commanding individual squad members, you build up your base, buy units/vehicles, assign units to squads, and then send those squads into the battle.