Depends on which faction I am playing. As a Roman faction, I tend to have a std. mix of equal parts cohort/archer/cav. This gets modified to fit a particular opponent. For the Eastern factions I go heavier on cav (and I save my most experienced Equites for this even after 'Uncle Marius' shows up). For the I throw in some Velite Glads to deal with the heavy chariots and go a bit more archer-heavy to shoot up those pesky chariot-archers, and for phalanx-heavy factions I go for more cohorts and heavy cav.

As an Eastern faction, I don't even bother with infantry in the later stages. I recruit some War Elephants, throw in substantial cataphract cav, heavy chariots, and merc Arab cav (my personal fav). With Pontus, there's the added benefit of Pontic HC.

With Carthage, War Elephants, plenty of Long Shield Cav, and Sacred Band. What else do you need

As a Barbarian faction, lots of heavy infantry (Gaul/Germany/Dacia/Thracia), lots of archers (Chosen Archers & Forester Warbands rock!) and merc Sarmatians for cav.

I tend to pepper the oncoming enemy with archers or 'spear-chuckers' before melee begins to thin out enemy infantry, and I try as much as possible to hit them from several directions at once, even if that means splitting my forces in the face of superior numbers (usually not a good idea).

With an all-cav + elephant set-up, I never wait for the enemy to reach me unless I'm sitting atop a big, fat hill. I'll charge them before they can get set up and use superior mobility to outmaneuver them.

Sadly, however, the mapmakers for RTW must not have played STW or MTW much because the opportunities to set traps are really restricted by 'cookie-cutter' maps that tend to be similar in form....usually hills in the corners, some forest or rough terrain thrown down in the middle, and an occasional rock or building plopped down in the very center