I agree,
I find MP so entertaining and it needs to be discussed more, the characters you run into are unreal. I once had a player accuse me of cheating because I assumed a computer who had 6 cities and created a 12 musket stack in 2 turns. (I drafted)
My strategy?
Unless you're on a HUGE island map, sharpen your blade.
The best strategy I know of is pillaging, and 90% of the time razing cities when you capture them. its all about starving your enemy and forcing your war machine on his.
I know alot of people are going to call this ******ed but after I get my initial cities worked properly I put my workers on Automate. When you're controlling 15+ units on a blazing timer in the ancient era you don't have much time for anything else. Also, the que command has become my best friend.
Once the Ancient/classic era has passed and the n00bs have been weeded out, I take them (workers) off automate and specialize my cities for optimum production, because then its usually an arms race that goes into the mid/ren. Then usually another big war.
Most games I play don't go past that but when they do (conts with 2/3 big civs left) it usually turns into a science race, due in part to the production already being there and everyone wants advance units.
Then, on the rear occasions when it happens: the modern/nuke war,! (which is an absolute blast)
Ok I'm ranting, I truly love civ4 mp, it's a 180 from sp, all the single player articles in the world wont save you in mp from a competent player.
(now for an actual strategy)
Landing behind the enemies main forces (via water) to destroy their core cities. Seriously, I know some people would all say "duh" to this, but you have no idea hoe many times this works.
For example, in the game I note above (12 musket stack) I assumed a computer civ that was on the verge of being destroyed. a human player had 60% of the map when I joined and close to 30 units on my border. I had the tech advantage as he had concentrated on military, so I kept drafting muskets to hold his ancient/classic army at bay while i produced gal/cav. made a landing on his core cities which were defended by war/arc. Razed 6 cities, he sent his main force back to save his city but it was to late, I was able to put a sizable force together on my front with him gone. The loss of his core cities effectively stopped his war machine, so I was able to beat his rather sizable army with mine on account that i was bringing up units to the front none stop (thank god the comp concentrates on only growth... draft FTW).
A prime example of why MP can be so much more dynamic then sp.
Also, I hear there are leagues for civ 4 mp, (which may have forums for strat) but they have rules like no war till 500BC which is lame.
anyways, thats my two cents, look forward to further discussion.