I use solid melee infantry to pin them down then flank with cavalry. Or alternatively take three or four units of archers; put them in front of my battle line on skirmish and fight large pointy sticks with small pointy sticks (that fly through the air at distance). This works well but be wary of heavily armoured enemy troops. The Phalanx formation is too slow to be able to deal with decent skirmishers, so try to break the formation and flanking of some kind is essential.

*Ringo*