Rule #1: When you see a tank. Better find the deepest hole you can find and pray it doesn't become your grave.
Rule #2: If you have an Anti-Tank weapon. FOR THE LOVE OF GOD DON'T WASTE IT FIRING AT A TANK HEAD ON! Or will have to resort to going to Rule #1.
Rule #3: Best have some good ear protection being around a tank or will go deaf. And also be killed by the recoil by mistake standing too close. Trust me.
Depends on the tank. That works for all modern Western and Russian tanks. If you're up against an older model without thermal imaging, and you're in restricted terrain, sneakery might net you a mission kill.