I think Rome 1 usually told you to put light infantry as your main line and flank with heavy, but that's ass-backwards. This may sound tedious most of the time, but keeping your troops from uselessly hurling missiles at shields so they can punish the enemy with javs/missiles late into a battle is a huge advantage. If that's not possible, then try to counter-charge. If you're not charging, then make sure you're braced or using a skill like spear wall to mitigate an enemy charge, as a charging unit gets combat bonuses from a successful charge.
Either way, some basic tips I can lend you: They're not as disparate as in Warhammer, but something like Parthia will obviously play differently from Rome.
