Game oriented usage of Lua?

[Jeroen Janssen <japj@...>]

I was wondering what the most/best used method of using Lua in a game
engine is/could be.

do you call several lua scripts & functions from C/C++ when entering a
specific gamestate?  (thus C/C++ contains you "main-game-loop")

or do you call a lua script that implements a "main-game-loop" (calling Lua
& C/C++ functions in the progress when entering a gamestate)

how far is lua being customized? :

do you use lua "out-of-the-box" or do you add specific features to lua not
available in the normal distributions 
(i.e. I know that Grim Fandanga adds some form of tasks to the lua language).

and how about maintaing different lua states? multithreading?

Best regards,

Jeroen Janssen