There are a number of real military resources.
Have a google for army field manuals. america has put many of them online.
or the 7 Questions (British).
Basically:
What is the situation and how does it affect me?
What have I been told to do and why?
What effects do I need to achieve and what direction must I give to develop my plan?
Where can I best accomplish each action or effect?
What resources do I need to accomplish each action or effect?
When and where do these actions take place in relation to each other?
What control measures do I need to impose?
I think that is more for small units but can work for large scale.
What is your objective? What are you trying to achieve? Unit destruction? conquest of territory? conquest of resource centres?
What resources do you have to achieve it.
How can your assets best be used.
Consider the terrain, and enemy strengths.
You know that a vital part of your campaign will require the capture of railways, and railyards.
Many of those are also resource production / Manpower production vital to russia.
Victory points of objectives should guide you.
Also important is the pocketing of enemy forces to cripple his manpower and equipment.
I dont think deception is effective on the AI, but...
The big problem is that all the military manuals are very vague, general principles, as a vast amount depends on objectives, equipment capability, enemy intentions etc.
Sun Tzu is still valid, but is not a direct instruction as to how to win WITE2 as German
You are very likely to find that if you do this seriously, then your plans are very likely to be close to what happened in history, as terrain, transport links and vital enemy cities / resources may not move much over time, and you have some understanding of the strengths and capabilities of your forces and the enemy forces.
Sneaking over mountains / forests (The ardennes) / bottlenecks can work if you surprise an enemy, but are also very risky and prone to failure if discovered, and you can be stopped by limited forces.
Identify strong defensive points, eg rivers.
Your aims will often be to break through a defence line, and take the next bridge / river crossing / strong defensive point on the bounce.
Military terms such as Manoevre warfare - break through and go round the enemy rather than fighting more pitched battles than needed.
Combined arms - basically using air, artillery, cavalry, armour and infantry in a combined attack to make the best of the capabilities.
What shortages do you have? as German reinforcements will be low, so you have to try not to waste valuable aircraft / artillery / armour.
Using artillery to break positions is great, if you are american, and have unlimited supply, but do you have the supply needed to bring up ammo and supply for artillery units?
Same with air. Are they an efficient use of your limited supplies.
It probably means identifying strategic goals, eg Moscow, Leningrad.
Identifying how you are going to defeat the enemy defence plan and supply your forces through each stage.
Dislaimer:
Don't claim to be on top of any of this, reading those pamphlets is mostly greek to me!
Someone with more patience than me might give a link to the army planning document for higher operations, but they are not very easy to read.
