I hope he doesn't mind me sharing it, but here is some great advice from Elda King:
The first thing we were doing was the civs, but we messed up a bit when we made a few UUs, buildings and other things. I sugest focusing a lot, and dividing the files among everyone instead of many people editing the same file. Oh, and one of the hardest parts of civ design is the diplo files; it can crack the whole mod and requires a lot of work. I sugest using regular diplo from the game (for example, make each leader use diplo from one vanilla leader - this way is good because later you can only use Find->Replace All to change all references at once), and then replace it as you make it.
About the comps, they probably should wait a little; they are not crucial. The quest is somewhat simpler if we are using itens from FFH, I believe - it's just a matter of making one event to create them, and giving them one ability like those of Great People (build something, give culture, etc). The "selective invisibility" could be hard, but if there are no Great Spies we could use this system.
The avatars predate the idea of king units, but they really work well together. It's great because it could be used for other units as well, like Gandalf or Glorfindel. It's also probably very simple to make - simply create a counter, and then spawn a unit.
!
That is just cruel man. 
