Sup guys. I was wondering for all you war mongerers, how you go about building your war machine. One problem I have is early in the game, most of my cities to pump out units fast enough. Even later on, I still can't compete with the computer when it comes to units. So what do you guys do to give yourself that extra edge? Do you just build all mines in one city? If you do, how do you keep your civs from starving? Thx in advance guys!

Even later on, I still can't compete with the computer when it comes to units.
The AI gets, at least, bonuses in military support and, at higher levels, significant bonuses in production. By the time you can keep up with the AI in sheer numbers you've already won the game. Successful warmongering means doing more with less. You need to use counters, promotions, bombardment, and terrain to achieve high kill ratios. I'm not a great warmonger yet, but on Monarch I like to hit about an 8:1 kill ratio, including suicide siege weapons. In many cases the first 5 turns of a war involve me defending against huge stacks of AI pillagers, where I might kill 40 units and lose 10-15. Once that initial surge is over, you can start using superior tactics and production to your advantage and lose basically nothing but siege weapons from there on out.

You did not say what level you were playing on...

Anyway, you have to determine what buildings you want to have built and focus on only military units.

You may need to focus on manually moving workers. A faster population growth means more production latter.

Well, I don't really know what level you're playing on, but I think this advice is pretty much universal. If you want a fast/heavy army just expand until you have a decent resource (iron if you can get it, but bronze or horses will do) and they start chop-rushing as many military units as you can. Use these units to kills someone and take over thier empire. Use the new cities you've taken to make more units. Repeat.

As long as you don't expand so fast that you ruin your economy this strategy, if played right, is good for almost a sure win on all but the highest difficulty levels.

Oh. I am playing on Noble.

You have to determine what era you want to push out units as well. For Romans, you can do what dangerous monkey is saying. Latter on, you can heavily irigate and pop rush units...