Common coding rules for directories and dependencies?

Hi!

Currently I am trying to develop features for international keyboards (http://forum.xbmc.org/showthread.php?p=1...post138013).

XBMC-Team wants to get "good" modules/only few/correct dependencies. But what are your "common" rules?

Some things are obvious, but other are not, e.g. may classes in guilib/common have dependencies to other directories? (Why (not)?)

What are the rules of the directories? Where should go what?

Which dependencies are allowed and forbidden?

Can you give a guideline for developers? (Should the answer go to this forum or to the wiki?)