when besieging a town (or large town) and the enemy sallies I tend to use my rams like a wall ..
i form a line like this:

< < < < <

< - ram (small caps between rams)

this prevents the enemy to attack my troops directly and will destroy there formation (very good thing if your enemy have lots of phalanxes) .. put your heavier troops on the flanks so you could destroy any flanking enemy units and in the middle some missile troops with units that can hold the line for some time .. when enemy finally attacks your troops you will have heavy infantry to attack there rears .. soon you will see a mass rout ..

have tried his both in vanilla and eb .. it works very well with romans but with others i'm not sure ...

also against cavalry heavy armies (HA and stuff) it probably doesn't work