im not sure about retraining the fleet, is your city under siege?
nothing retrains or builds when sieged.
you got the star because the place you built them in had a general commanding with some 'seamanship' quality or something i think.
yeah, my battle formation for any country is infantry line with archers behind, cavelry at sides.
although the greek horses suck big time so when greek i have additional infantry holding the flanks.
essentially i make an impenatrable box that holds my archers in saftey. not much in the way of AI can beat it except with serious numbers or very well trained troops.
for offensive, i LOVE the onagers. nothing like a few firery balls of death flying at the enemy to weaken their resolve
attacking stone walls:get some onagers and destroy the gate house and any towers that may be a threat to your possition. next take some ladders round the side or back walls and get some missle troops up them.
once on the wall you can run right round the defences capturing all their towers. once youve done this you can hold the defences on the front wall at bay while you get your infantry up the ladders in saftey. should any enemy try to stop you....well you took their towers so they fire inwards apon them now

also your archers/spears can rain terror on them from any posstion you like with little to no chance of taking casualties themsleves.
i also would say VH/VH difficulty is the most rewarding after a few campaigns.
cant wait to play online, a real opponent would be awesome, and very difficult at first i imagine.