I try to be middle of the road myself. Defensive is always a good idea, but I like to get things DONE, so I'll just send half my army out into the fray while the other guards whatever needs guarding.

...that actually sounds kinda fun. >:D I like sending out my more badass units and watching enemies kill themselves against them (Aless vs the Mage Sisters in FE4, fliers with javelins against any archer). Or in the case of certain spoony bards/dancers, watch the enemy keep missing against them!