If the tanks on patrol (for example, in Market Garden or Neptune) seem like they are chasing you and you cannot get a good shooting position, aim for their caterpillar tracks. This works best with a recoilless rifle or a Panzerschreck, but Gammon grenades will also work if you are skilled with them. With either of the rocket launchers, aim directly at the gears of the tracks and put a round through it. The tank will stop, making it much easier to get ammo to take it out. With the Gammon grenades, throwing it directly up against the tracks or cook it so it bursts on contact or in the air next to it.