Watchtower battle

If its on the campaign map it shows up on the battlefield. Well it was a small battle with 2 rebel units. The only thing was they took over the watchtowers ramparts wich had a 70 degree slope. You can comfortably fit about 4-6 units on this nice little battlefield obstacle. Well normally those 70 degree slopes are a bit unrealistic but in this cass it made sense.

But if I know a big armie is coming now I know to camp right next to a watchtower for a little extra defensive positioning and place the archers up there who WO'NT HIT my own troops

That's very nice to know.
Generally using elevations strongly decreases the friendly fire effect.
I put my archers on the top of a hill, usually first in front of the spears.
Javelin-Skirmishers even more in front. Slingers I put in the foremost line, slightly to the flanks. It's important that you watch the slingers to prevent friendly fire. They can be really devastating.
Yesterday, with this setup, I awaited a Seleucid army of mainly pahlanxes.
They didn't even make contact with my lines. Fiery and stony death rained upon them until they routed.

R'as