How do I start up my own game development company and how do game
development companies run?

Hmm, let's see.
All you need is about $200,000 give or take to buy the rights
to use a game engine, or hire a team of high-paid programmers
to build one for you.


Information about buying the Unreal Engine for making and
selling games and what's required to even apply go to:

http://www.unrealtechnology.com/


For an idea of how actual game development works,
EpicGames provides a large amount of documentation on how to
modify Unreal Tournament.

http://udn.epicgames.com/ - Epic's Unreal Development Network
http://www.masteringunreal.com/ - 3DBuzz's free online classes and video tutorials

Or you could just make mods and get hired by some company,
or even win $1,000,000 mod contest EpicGames is having.