To coordinate well with your team, get mumble, which is totally awesome. If you can not use mumble because of tech issues or because you are simply an antimublist, make extensive use of the squadleder Radio to mark threats to the armor and targets.
A guide for AAS maps
The armor should stick with infantry units at all time. If the armor is out on its own the enemy either avoids the armor, or is suppressed, however a suppressed enemy with no ground troops around to take advantage does the team no good. Then there is the increased threat of handhelt AT weapons.
RIGHT
WRONG 
If Infantery is moving with a tank or APC they should stick with it as much as possible. Do not run off with your squad cutting through the forest, unless it is to take out a nearby fob or the actual objective is there. Do not take the route that offers the best cover, but take a route on which the tank can follow you. If there is trouble there is always the tank to keep the heads of the enemies down.
Likewise the armor should stay behind friendlies, Use the full speed of the armor to redeploy, but when supporting an Infantery squad dont rush ahead to find out if thats a TOW in the distance. Let the Infantery take out AT gunners so you can operate safely.
RIGHT
WRONG 
As a squadleader your first priority before calling in support is to look for threats to your armor. Have the tank pull up to a safe area, target enemy AT Call in the Tank to blow up the now unmanned enemy AT and have it cover your Advance Afterwards. Same if you attack a flag, scout out the area and mark as many targets as possible before haveint the tank roll in.

If you are holding an objective dont have the armor sitting on the objective with you. The enemy could take it out with AT weapons before you even know they arrived. Have the tank wait in a safe area and call it in as needed.
RIGHT
WRONG
When fighting an unconventional war you need to consider that because there are no frontlines, threats to Armor are much more unpredictable. While Infantry is generally engaged by enemy infantery on AAS maps, even if the squad carries AT weapons, Insurgents might have dedicated AT teams, which might not give themselves away by opening fire on accompanying infantry, but target the armor right away.
Armor should wait in a safe area with open ground it can overwatch easily, assit infantery as it is called in and retreat back to a safe area after the squad medicated its wounded. Do not stick around, because the enemy will plot on how to take down an armored piece if it is in a vulnerable position.
RIGHT
WRONG 
When entering a reclusive area on an isurgency map, avoid entering it at areas which are nearby enemy strongholds, because it is likely they are camping entries and exits nearby to their weapons caches.
RIGHT
WRONG

EDIT: Basically if you run armor ask an infantery squad to cooperate with you, lead the way and clear the sides of the roads, if you run an infantery squad, see if some armor is willing to trail you.


