here is an example Germany 36 game: Take all your ground units exept I. Armeekorps in preussia, Berlin Hq in berlin, and Hamburg Hq, and move them to leipzig. Remove them from your Theatres, but keep the Corpses as they are. Now you got 9 corps (i think), and an army group HQ in leipzig. Now click a corps HQ, and push the "create Army" button. Assign 4 more corps to the 1st army. Then you click on one of the corpses that is unassigned and create another army. Assign those corpses left to the 2nd Army. Now you click on the 1st army, and push the "create army group button". Call it something Like Army group North or as you please. (Heeresgruppe Nord). And assign this to Berlin HQ. The 2nd army you attach to the already existing Heeresgruppe A (army group). Heeresgruppe A you attach to Hamburg HQ. (I prefere names Like Heeresgruppe West, or something else that tells me were the units belong.) Now you should have a good platform to build from.
Just fill up those Army groups with Armies, and your Armies with corpses. Now you should assign most of your forces that you are currently training to Heeresgruppe Nord facing northern Poland. Only a few divisions or corpses more are needed to defend against France during the attack on poland. Remember to create another armygroup(Army group South) and deploy som units there, (preferably 2 full Armys) to go for southern Poland.
Short: Have each Corps filled up with atleast 3 divisions, Have each Army filled Up with atleast 3 corps And each Army group should have some Armys attached. And remember to consentrate your Armoured forces, not have one Armoured division here and there like the French did. Make own "Panzerkorps" and "Panzerarmee"`s
wich contains armoured and motorised divisions to use as breakthrough troops.
When it comes to Airforce management i do like this in the beginning:
Take all your fighters to Kassel, and group them in Fliegerkorps of two fighters each. Take all your bombers to Breslau and group them in Luftflottes of 3 or 4 each. I like to give them names so i can easy see what they contain. for example fighters you can call Fliegerkorps and bombers you can call Luftflotte.
Dont ever use more than 4. Air unist together, as you will recieve a very high stacking penalty.
And DONT let the AI Touch your airforce, remove them from any theatre, same goes for your naval forces.
PS: Sorry for bad english.
MauserM98