Early Game, Mid Game, and End Game... What's the goal of each?

[Psitticine]

I think you've got the right basic idea, at least IMO. Personally, I'd define the nature of the 3 stages as follows:

EARLY GAME - Securing resources for future use

MIDDLE GAME - Developing resources, research, etc. and pressing against weak enemies

END GAME - Bringing developed power to bear against the tougher opponents

Each game varies a lot, however. Last "big" game I played denied me anything that I'd consider an early game. I started between two powerful opponents and had to strike out at one before becoming pinned in. It was full-out, open war from Turn 1, and I was always too busy scrambling to keep others off my back to really spare anything more than a few crumbs for development or plotting for the future.