I like wars too.
Some excellent advice here - for example, it took me awhile to learn that 4 or 5 techs behind is ok (it means that they're cheaper!) and early wars can cut dangerous opponents down to size.
I've been experimenting with very early pillaging wars, like the Jag rush or Gallic Swords. Scout your nearest/strongest neighbor and plan your first war before things develop: does he have iron or horses? What's his UU and how can you prevent him building any? Find and prepare to disconnect the dangerous resource. If you can restrict him to building archers while you have fast units running around cutting his roads and destroying his infrastructure, his workers will be hiding in cities while yours are developing your empire. Speed is golden. With it, you can pick and choose your battles and terrain, concentrate where and when you want, and often retreat away from death.
Jags and Impi can't really take his cities, but I'm suggesting that you don't need to - if you lay waste to his empire convincingly, destroy his mines and irrigation, prevent his workers from working, soon he'll give you some techs for peace. If you can thus weaken one of your opponents, then during the 20 turns of peace do it to another, when you return to the first one, you can probably start taking cities and resources. Note that an advanced tech like Chivalry does him no good if you've cut his horses. (Exception: India.)
It's essential to keep him from making alliances against you. Get Writing quickly and Embassies with anyone close enough to matter. You want RoPs and Politeness with everyone (except the current target.) Trade early and often with his neighbors. Make friends and influence civs.
The larger the map, the more important is the Great Library: to capture, not build! In fact, the higher the difficulty, the better it is to capture Wonders.
Later wars, when you're facing stronger weapons, artillery looks delicious. The more, the better.
And Armies too: develop and protect your Veterans and Elites. Do NOT waste Elites by letting them be killed - you want each to fight and win until they spawn their rightful Leader.