MW2 Lessons?

Hey..I heard some people talking about lessons in a lobby earlier...I had a few questions about it..here are some of them

wth can you teach in MW2 that isnt common sense?
-No Scope/Quick Scopes? - How do you "Teach" that to someone?
-What setups to use? - Doesn't your setup depends upon the way you play as an individual?
-Callouts? Maybe? Isnt that just common sense though?

Idk..This isnt a sale or anything just something about xbox I was curious about..If its bad or in the wrong spot..I really dgaf but dont get butt hurt over it please.