To be honest, it's no good being commander if you don't have any good squads to support you. Also, don't bother trying to be commander if you're losing badly and it's already halfway through the round. You won't make much difference, if at all.
You should be using arty constantly - BUT never use it if you have your own team members nearby, or tell them to get the hell out the way.
Rule is: bombard, bombard, bombard. You *have* to keep them busy. If you've got nothing to bombard, do a scan, find the solitary dot in the middle of nowhere, and send an arty there - 9 times out of 10 you've just nailed the enemy commander.

I find it as funny as hell, especially when the commander suddenly has a personal vendetta against you and personally comes after your @ss.
Send supply drops to the guys that ask for it. If they don't ask, drop it near occupied armor, it will help repair them, and supply them with more ammo if they need it - like mobile AA.
If your equipment such as arty, radar, or uav trailer gets blown, drop a supply crate nearby, it will get repaired. It gets really annoying if they constantly blow your equipment tho - the supply crate drop takes awhile to regenerate.
Also, if you're planning on being commander, spawn as engineer, and be somewhere near your equipment so that you can repair it if necessary. Stay hidden though.
Keep your UAVs flying. If you're not sure where to drop it, do a scan to see the location of heavy enemy activity, and drop a UAV there. In the mean time, your scan will regen. As soon as the UAV is finished, do another scan. By the time the scan is complete, your UAV should be ready again.
Although I'm quite bad at it, keep in touch with your squad leaders, let them know about incoming armor etc, but DON'T spot all the time, cuz 'enemy troops spotted' gets really annoying after the millionth time from the commander.
If you see snipers, spot them, sure, cuz they're annoying buggers. Arty them if necessary.
Something to remember, if you're commander, and you're not in top-down view, if you're running around with other players, you can use the secondary radio (T) to drop UAVS and supplies etc to your position.