Marching in ranks three deep may have worked in the Civil War (barely) and times prior, but won't pass muster in WWII. Despite the fact that most public battles feel more like a giant game of leapfrog, it is still important in better battles or tactical scenarios that we have some sort of accurate representation of what would have happened.
First off, pretend the Germans are shooting live rounds. Forget the shells and explosions from artillery, tanks, mortars, and grenades and just focus in on bullets. You don't want to get hit with one of those things (it just might sting a bit). Now pretend you're in an open field. Where is the best place to be? Face in the dirt behind whatever cover is available that has a chance of stopping a bullet, even a slight rise in the ground might do. Lets face it, you don't want to die, so you'll do just about everything to increase your odds of living.
If reenactors started firing live rounds, we would all be dead and rapidly learn from the units that were wiped out (probably airborne and FJ units) that being in the open, behind bushes, or small trees will not save your life. Over time units would learn that advancing through an open field when there is a perfectly good wood line isn't good either. We'd discover that rifles can and will throw lead as far as you can see and that nothing short of a massive red wood, boulder, or thick metal is going to stop that round. Lets not even speak of the 75mm rounds that are flying around and the hand grenades that are tossed about also. Basically, the handful of units left are going to be those that a) learn quickly, b) work as a team, and c) read this section.
Why the long tirade? Only to make a few simple points to those reenacting. Get down and crawl. Take cover. Work as a unit. Take hits.
All sections, except the "As a Unit" section, assume you are working alone. The rules and guidelines herein will generally apply even while moving as a unit. As a unit, more considerations must be made. The sections are as follows.