Get a Faust before going to Moody's position. Take out the tank just when it appears to cause your men to run headlong back to the church. The gate will not come down and the house and fence will not explode. This usually results in them getting slaughtered by the two or three Nazis standing guard.
Lean from the wall to get rid of the two MG42S guarding the first flak gun. Doing so will cause a new machine gunner to spawn, but your men will charge forward anyway, leading to a huge pile up of bodies and extra BAR ammunition. Your men will eventually take out the extra gunner.
In the field when you begin the level, charge forward past the three MG42s in the windows and sandbag. Note: This is best done under the easiest difficulty setting. Stand there without shooting anyone and your men will waste themselves on the 42s. If this is done long enough and with "insane body count", they will eventually stop spawning. You can do the same thing almost everywhere else there is a 42 and spawning men.
It is possible to save Johnson by running out with him. You can Faust the Panzer coming up either through the church window or, if you are very brave, by running out as fast as you can and reaching it before it gets to the barrier.
On the way back, right before you get to the truck, there are three ways to get back to Foley; the alley closest to you, the alley in between, and the alley furthermost from you. You can play around with the alleys and their triggers by running back to the common areas and going down another alley. By doing this, your men will get caught in a three way crossfire.
To get an MP 40 in the final mission, do not take the first one that you see. Instead, until you find the second MP 40 and take it. You will get about 500 rounds of ammo, which should be enough to complete the mission.
In Burnville (the second map), when you must go into the church to knock out the two machine gunners and the antiaircraft fire, do not go to the church. Instead, stay behind the big tomb with a cross on it and toss grenades over the wall to where the two machine gunners and antiaircraft guns would be (the corner of where the walls meet above it). Keep throwing them until someone says "Way to chuck, Private".