Big fan of this free new Arma 2 mod called Project Reality aka ‘PR’.
Download it from here:
http://www.realitymod.com
These 9 YouTube videos provide excellent gameplay Tutorials. Watch them and re-watch them and experiment for yourself. Maybe fool around on an empty PR server.
I usually play on the TG (Tactical Gamer) PR server or the BigD & AEF PR server.