I'd say a general knowledge of tactics and strategy are important. How you gain this knowledge isn't really material. You could learn it from a friend, reviewing old wars or simply reading wikipedia.
Many basic concepts of war apply to the table top such as proper positioning, fire lanes, cover usage, overlapping unit support and overwhelming force.
Other concepts like logistical support obviously have no impact.
In this thread there have been several people claiming that due to the dependence on dice that tactics and strategy don't play in the game. That's completely untrue.
Tactics, in a
40k setting, boils down to what a particular unit is going to do on their turn. Strategy is the overall goal of the entire army during the game. If you have an objective game but your strategy doesn't allow for claiming or denying objectives then you will lose. If you have a unit 6" away from an unclaimed objective at the bottom of turn 5 and decide to charge an enemy further away then you'll lose more often than not due to bad tactics. (Review the charge of the Light Horse brigade)
You might call that common sense; however, the real world terms are more appropriate.
Going along with other known military doctrines:
If you have no idea what your opponents army can do then you will not be able to properly counter it and you will lose. This is analogous with using Military Intelligence.
Further, certain military formations might also be helpful. Such as the
Flying Wedge. We often call this "bubble wrapping", but it's the same thing. Protecting a center while providing the best fire and assault arcs available. It's further interesting in how it can cause a gun line to roll up around an assaulting unit. Especially helpful if an objective is behind the line and you have two units involved. The first to pull the gun line out the second to run past them.
Point is, don't discount 2000+ years of warfare simply because you think it might not apply. Some of it most certainly does.
