One of my biggest complaints about reenactors is that many of them are not realy awaire of the tactics used by armies of the period. This is due in part to the fact that (at least for the Germans) Reference books are not available or in the right language. A little digging however will uncover a wealth of information form a few simple sources. The best source is U.S. Army or U.K. documents form the period that deal with German tactics. While the originals may not be available in large numbers there has been a reprint of the U.S. Army handbook on German Military Forces.
Another problem with reenactors is a general lack of training. It's not too difficult to understand the tactics of the day and still not be able to apply thing to the battle. A good example is when was the last time you were asked to perform a reconassence patrol, set up a road block or outpost. These are all routine tasks of a normal soldier but the tactics are never employed. That is mostly due to the fact that very few reenactments have any kind of command structure.
With that in mind here is how a typical German Defensive line should look.
5,000 to 7,000 meters from the Hauptkampffeld (Main Line of Resestance) a Vorgeschobene Stellung (Advanced Position) is set up. Since these units are too far from the MLR they must be very moble. They will probably be composed of Divisional Recon detachements and are supported by artillery fire only.
Next is the Vorposten which is 2,000 to 5,000 meters to the front of the MLR, however it must be covered by the supporting fire of the MLR. Since very few reenactment units have 12 cm morters or 7.5cm infantry guns the vorposten sould not be beyond the range of the parent units fire 100-200 meters.