Warbands would be the common formation. The greek/etruscan influence probably means they were more disciplined than some cultures (ie - they could keep a straight line) but the tactics would have been somewhat primitive compared to later periods. A more individualistic 'heroic' style of combat would have occurred. We see this sort of thing in the tale of Horatius guarding the bridge.
Another fact is when using cavalry they used the common for that era, two horse carriage with a bowman and a driver in the chariot.