You can make other factions declare war on each other by giving them enough to make it worthwhile. This can be very effective.

While playing as the Greeks, I managed to get the Dacians, Thracians and Macedonians all attack the Brutii, thus keeping them out of my hair.

The funny thing is that I'm now fully in control of Greece (Macedonia holds only the nothernmost of it's original cities, plus two former rebel cities), and have several cities in Asia Minor and Africa (taken from rebels). However, I have still to fight a single battle against the Romans.

I got a trade agreements with most of the other factions including the three Roman houses, and alliances with Egypt and Pontus.

Come to think of it, I have only been at war with Macedonia so far, and then only for about 8 turns.