Strategy is the approach of the use of the army as a hole. Once we know how units work we can design armies in such a way that all of them act together to achieve one common goal: to defeat the enemy. If we are already superior in numbers and quality, there's no merit at all on winning a battle. It's in equality or disadvantage situtions when the planification of the army and the planification of the battle gain in importance.
The planification of the battle can only be done once we've seen the enemy army and the battlefield, and it should be in harmony with the planification of the army. Moreover, once the battle has started, we will have only some seconds to sketch it's course, so it has to be something simple and effective. Complicated strategies often fail because they are difficult to implement; the require too unit management.
Strategies in this section belong to the realm of army planification. Furthermore, they are of general purpose. If we know the factions we are facing we can and should design the army having this in mind to exploit their weaker points.
Finally, there are two general rules when designing the army and planifying the battle. First, you should always try to have the maximum number of available units, i.e., all the unit slots used. If we have less units than our foe we could be easily outflanked and that's something we want to avoid (I think in Warhammer games this isn't so critical). Second, don't leave holes in your lines. This also includes not leaving gaps between your lines and your allies' ones on multiplayer games. Gaps can be used by the enemies to kill your missile units and rearcharge you, and that's something you want to avoid.
Note: when I talk in this page of gaps, I mean big gaps, that enemy cavalry can use to flank us. The gaps that I talk about on missile infantry sections are small gaps that can't be used by enemy cavalry for this purpose.