What's metagaming and how can it help my students?

A game usually takes place within what Katie Salen calls a "magic circle" which refers to the space and /or time where the game is played. 

When the game is over, the players physically and metaphorically step outside of this circle: they put away the cards, dice, board, ball, tablet, phone and get on with "real" life.  When the game is over in EFL class, sadly, students go back to their seats, open up their grammar books and go back to "work".

But what if you could extend the game, have it sneak its tentacles outside the magic circle and invade the space and time between games? 

Richard Garfield wrote an essay called "Metagames" http://ludusmechanicus.files.wordpress.com/2009/11/garfield.pdf
in which he focusses on 4 questions which, for language teachers, can be especially interesting to think about:

1. What a player brings to a game: 
What language (grammar, vocabulary, idioms etc) do the players already know?  What are their expectations of an EFL game?  Have their previous experiences with EFL games been good or merely a way to get out of a boring grammar lesson?  What mood are they in? etc. 

2. What a player takes away from a game:
Have the players learned something new during the game or was it designed to practice what they already knew?  Was the theme or topic of the game new?  Did they gain a deeper insight into a social phenomenon or come away with a different image of themselves? etc.

3. What happens between games:
Did the players prepare anything for the game?  Did they design the game itself?  What did they have to know in order to do that?

4. What happens during a game other than the game itself:
Whatever communication happens between the players during the game is an opportunity to teach and to assess their knowledge of English...and in fact because they're in a position where they need to know, we as teachers are in the perfect position to really help them learn.