What does game "depth" really mean?

"- Be one step ahead of your enemy (i.e.: if he knows that you go always that route to get the next powerup, but you also know that he knows it, you take this time another route to surprise him)"

This is an important thought process, I think in xonotic if I play actively as I did back in 2005-2007/08 in nexuiz, I can think like this but it takes a LOT of time and practice..this is like REALLY deep thought-processing though and only something I learnt in the past few years I don't expect any intermediate player to think like this long-term. In poker they call it 'Meta-game' I believe, atleast in headsup poker, basically you know your opponent is competent, he knows you are, it's all about not just watching his play but remembering what your opponent thought or did when you did decision A, and then changing that perception for the next time so like bundy said you know your opponent knows you normally go one way, so you go another way..this gives you a edge even if it's just slight..I think I started talking about stuff like this with PCLizard.

I guess I really should take some time to write a guide, however I don't really want to do it until Xonotic is released otherwise it'll be based off nexuiz.