Sryth,
Just to echo Galileo44 ...
Welcome to CivFanatics!
Certainly I agree with Galileo44 that seige weaponary is vitally important during this time; Catapults - and if Warlords; Trebuchets - each play an important role in bringing down city defenses with their bombard ability, and then afterwards delivering collateral damage. You may be familiar with the phrase "suicide cats" - which are Catapults used with the specific intention of delivering collateral damage (after you've brought down the city defenses), with little chance of survival. Eventually you can reduce the enemys' units down to 50% of thier strength, and then your Macemen or War Elephants or whoever can go in and take the city. There's no doubt that Longbows fortified on a city in a hill can be a real pain to take out, so prepare for losses.
Try to take the city in the one turn - the last thing you want is letting the defenders get promoted and/or healed between turns.
In terms of being attacked, I would try to keep the diplomatic relations as positive as practicable with select neighbours. Be wary of adopting a religion of contrasting faith to a neighbour unless you're confident that they won't be any realistic threat to you. Consider trading with only your 'chums' and neutral civs if you must - and be wary of their relationships with each other; you don't want to have negative modifiers for trading with their worst enemy while trying to curry favour with another 'chum'. Be mindful of the varying behaviours of the different leaders (e.g. Alexander the backstabber, Qin Shi Huang the backstabber, Tokugawa the isolationist, Julius Caesar the backstabber, Isabella the religious fanatic, Napolean the backstabber, etc.

). Put a half-decent garrison in coastal cities and border cities, and even consider having some 2-move units on hand to be able to shoot over to problem areas. Have 'unit pump' cities to support the others. If possible, keep a few hundred

in the reserve in case you need a couple of instant upgrades in response to a surprise attack.
I hope this is of some use. Enjoy!
