Strategy for Fall Blau
As the Germans, you start off with a better army in the field, but it will quickly lose its advantages as the soveits gain reinforcements and retreat to more favorable terrain and weather. Time is critical on this map, as it will be difficult to score any big wins once the ground freezes. You have until November 18th to get 130 VP which is pretty much all of them.
Get all your forces to the front, especially aircraft which will be critical in making breakthroughs and killing divisions with ground attack. The army groups on the front are pretty well aranged, but you will want to consolidate some armies, and regroup them in more appropriate ways. Also, Manstein begins in the Crimea, and once Sevastopol falls he should be redeployed to a central location.
Start by attacking Sevastopol, it should fall by day 2, and it will free up several good divisions and commanders for more important theaters. Just go at it and keep hitting it until it falls. If your first attack fails, use aircraft for interdiction or logistical strike (to lower enemy ESE).
Next start by attacking the weak spots on the Soviet line where you can send armies from multiple provinces into a lightly defended area. On the first day, I recommend attacking north towards Orel, and east to Bilovodsk. Attacking these provences with all possible forces in the region should result in victory by the end to the first day, and it will route a large portion of the Soviet forces at the front, which will give you an advantage in the opening phase. If your battles drag on for more than a day then the Soviet reserves will arrive, and it will be a waste to continue the attack. The fact that the Soviet troops are set as reserves by default can be exploited, as you can lead their forces away from the key provences by launching feints at weaker ones.
Continue fighting battles like this, being sure to encircle and destroy soviet divisions, until you reach the Don, which really does slow you down, and limit your advance.
You can attack north towards Tula, and using it to flank the forces defending the river, but this is a slow way of crossing the river, and you end up with all your armies in the north, while all the major targets are in the south. Some good crossing points are at Svoboda, in the east which can be attacked from three provences, and allows a for strong eastward attack through plaines and Salsk in the South, which allows the caucuses to be cut off quckly. If the Soviets ever try to attack you across the river, try to muster a counter attack, and you will get a flanking bonus which negates the river crossing penalties.
Once the Don has been crossed, the Soviet lines should be thinned out a bit, and you can make more rapid advances. Head to Grozny in the south to cut off the Caucuses, allowing you to take Baku. In the north head eastward, the ultimate goal being Kuybyshev, which being the farthest VP province is the deciding factor for a strategic victory. A good crossing point over the Volga that will put you in striking distance of Kuybyachev is Engles. Another good idea, if the opportunity presents itself is to turn north and try to drive as many Soviet divisions as possible towards Gorkji were they will be trapped. This will take up some time, but it is one of the last good places for encirclements before the Volga, and if you can get a good number of armied holed up in the north, it will make going east that much easier.
From here you should be in a good place to wrap things up as the winter comes in. Try to avoid a city fight at stalingrad, as it will take time, just bypass it and run some interdiction missions. Remember that the Soviets get reinforcements at Stalingrad and Kuybyashev-two of the most vital provinces, so be sure to either occupy them quickly, or bring a large force (this is especially the case with Kuybyachev). Also be wary of Soviet Counter attacks in lightly defended VP provinces. Because you need every VP to win, and the loss of one minor province will cost you the game.
Be sure to not get slowed down on this map, you'll have to maintain a steady eastward advance to make it.