Playing as Commander, always try to think with strategy when ordering your forces. Keep in mind the enemy movements, commonly used enemy routes, and a quality tactic to lead your force to victory.
Don't just flank your enemies, bombard them and lower their will to play for their army. Use tactics such as the Pincer maneuver, and always support your teammates with supplies, vehicles to keep the advance going/resuppling areas in need of defense, and arty to "soften the attack zone."
These are really some of the best commander tactics I can come up with, besides try to always have an organized chain of command.
Also, eh, don't waste grenades unless you're in a despair situation (Such as being pinned down by an MG, and in such case only use rifle nades for better accuracy) or cannot take down a group of infantry due to a lack of fast firing weapon, that can react to the infantry seeing the direction of the rifleman who just took out their best friend.