I can only imagine that it would be pretty difficult to understand what is going on as each year of the war things were radically different.
If you are talking Western Front (U.S. and Brittish Forces vs Germans) you can pretty much assume that the Germans have superior firepower. Their tanks fired higher velocity and larger rounds than ours, and had far superior armor protection. So if you are playing the Allies, you will want to close the gap between your armor and theirs to increase your penetration. And if you are playing the Germans you will want to keep your distance and remain in a hull down position. (This is a generalization as a Pershing tank against a Panzer III would be the exact opposite situation but was an unlikely match-up during the war.)
If it’s early in the war, the Allied infantry are inexperienced (Dough Boys) and the Germans are typically battle hardened from the Russian front. If it’s late in the war the Germans are old men and young boys and the Allies are seasoned veterans.
Artillery of all sorts is best used as a way to weaken the morale of the enemy. And soften hardpoints. Units that are taking artillery fire will not advance and can often be flanked.
Start with small missions with a few units to get used to their strengths and weaknesses. Keep your leaders near your troops to keep their morale up. Use all your units as a team and concentrate your fire. If you divide your fire up against your opponents you’ll end up wasting ammo. By keeping teams together and firing on individual targets you will drop their morale much quicker and overtake them rapidly.
Don’t drive your tanks around by themselves thinking they are impervious to infantry. Just the opposite. They are better used to the rear so your infantry can flush out the ambushers and then you can mow them down with machine gun fire.
Of course, everyone’s tactics are different. Just some helpful suggestions there. You can always watch the Hitler channel (History) on cable. There is something on about the Nazis every night.