How do coaches teach tactics?

I was reading about Spassky last night and the book mentioned that Spassky's second coach, the imaginative attacking player Tolush, really helped Spassky learn tactics. I am curious, how do coaches teach tactics and combinations?

Bueller?        Beuller?

There's gotta be some undiscovered tactics on the chessboard. We all know the fork, skewer, pin, etc., but surely someone will find a spoon, a hammer or some other utensil.

interesting, i can see how if someone more skilled analyzed your games that would be helpful

One can but hope! 

Basically, there are two parts in tactics : spotting patterns (building blocks of intuition) and calculation.

For patterns, a coach might just throw some typical ideas when analyzing a game, showing patterns along the way, so that the student is exposed to them. However, that is only a complement to some necessary groundwork on learning basic patterns, which the student may already know, or not. This preliminary learning requires independent work, though the coach will probably suggest some good material and an efficient study method.

For calculation, that's something you can develop by actively trying to find the consequences of a tactical idea on the board. So simply exploring ideas while analyzing some GM game, without moving the pieces, is an excellent way to develop your calculation skills. There are also many complex positions which are useful for independant calculation training. A coach might use the analysis method during a session and provide the student with complementary exercises between sessions. There are also some calculation shortcuts that you can teach when you see how the student is building the tree of variations.