Mission: Understand the 'Mission'.
Enemy: the V key to get the enemy's point of view.
Troops: See which is + which is - they both have their uses. Support elements Artillery and Armour. Veteran and above I think spot better.
Terrain: Check eye level where the dead ground is. The less obvious the better. Walls, trees. bushes , buildings is what the enemy is using as references.
Time: Use it properly or you lose it.
Civilians: Find military targets. It pays to use your ammunition where you have not only full icon contact but fresh tentative contacts too.