Most games have built-in tutorial system. It is extremely important to teach people playing your game.
Of course your game should have intuitive design, not 5 buttons pressed at same time or stuff like this, but anyway after a long break there is a problem with common games:
You forget everything but game thinks that you previously learnt all the stuff according to game progress and not displaying tutorial again.
Games like Risen all the time displaying help according to game situation. It is very cool, but harder.
What if save previous game session real world time. And after entering new session calculate time difference between current and previous session and according to this information displaying game tutorial.
