Applying Techniques in Tutorials To preface, I've played chess a while but am just beginning to take it seriously in regards to the studying past games and different techniques. Bear with me as my question is a bit conceptual...

The big question I have is how to use these techniques correctly in a real world situation. Whenever you watch or read about certain types of games to play, the person teaches in a way that you just 'assume' the other person is going to make a certain move, then you make this move, etc etc. Obviously this is not realistic so I'm wondering if that means that the best players just absorb all of these different situations and adapt accordingly?

This seems improbable to me because of the near infinite possible ways a game can be played. Do the greats generally play the same way with slightly nuanced differences? How can one 'assume' what the other player is doing?

Knowing a little history, I believe it was game 3 of the Spassky/Fisher matches where Fisher played way outside of the box...did this throw Spassky off because he was so used to seeing certain moves?

I know I have a couple questions here but in general I'm just trying to find the best way to use tutorials and past matches in the real world.

Thanks!
It depends on what exactly the tutorial is trying to teach you.

If it is an opening tutorial, say about the Italian game, then obviously after 1.e4 black has any number of responses and you'll have to find a tutorial for each and every one of them. 

If the tutorial teaches you about certain strategic situations, then only the sensible responses will be examined, and what is sensible is something you'll learn by being exposed to many different positions and moves. See: How do players &quot;see&quot; several moves ahead?

If the tutorial touches upon a tactical position, for example a mating attack, then it makes a lot of sense for you to try to find the right way to continue if the opponent had made a different move. It'll probably have some easy refutation and you'll learn a lot by trying to find it by yourself.