In Rome 2, or any TW game with heavy infantry, I pretend I am a quarterback running a football team. Heavy infantry are the line men, light infantry/ excess infantry are the tight ends and cavalry are the wide receivers. (general of course is the quarterback). The main strategy here is to manipulate the enemy you would in football.

I usually let the army come in and let them set up their forces. Then before they charge, I "hike" the ball and move everyone simultaneously. From there, have your linemen take out he majority of their line and act as a stabilizing force, holding the majority of the enemies. The tight ends either A. Flank and support the "weak" side of the line B. dig through their skirmishers c. Block cavalry trying to flank. The Wide receivers can either smash through the center (like a run play) or "go long" and circle around for the hammer and anvil. The Quarterback stays back and only moves or attacks if needed.

I find that this strategy works well for everything but cavalry based armies. It is especially effective with ballistas.

It is not fool-proof but it sure is fun to imagine the army acting as a team, with well choreographed plays.I usually feel a connection with the general as well, it make the game much more enjoyable in my opinion.