How to learn tactics

(I'm talking about tactics from a book, I have no experience with tactical training software.)

Suppose you do a tactical puzzle, the outcome might be one of the following:

1. You solve it immediately.

2. You find the right move but are surprised by some alternative lines in the given answer.

3. You find the answer after a long time and still doubt if you would also have found it if this would have been your own OTB game.

4. You don't find the answer, but after reading the given answer you think "OMG why didn't I look at that??"

5. You don't find the answer, and it takes some serious effort to understand the given answer.

6. You don't find the answer, and after reading the given answer you still have no clue why that would be such a good move.

Which of these is the most beneficial for improving your tactical skills, and per scenario how should you proceed afterwards?

For my level of beginner/intermediate, it's 4. and 5., but mostly 4.

I don't spend more than a few minutes on a puzzle. If I don't get it, then I look at the solution. Make sure it makes sense. Then I move on to the next puzzle. 

Thanks zBorris.

I think for me, spending an hour on a difficult puzzle learns me to focus on calculating when really weird positions appear in my games.

To be honest I think it depends on your tactics level.  If you're not good tactically, going quickly and seeing the answer and moving on has the benefit of you seeing a lot of problems and starting to learn patterns.  As you get stronger it seems like looking deep helps improve your calculation depth and accuracy, and is as such more important.  Obviously not understanding the answer means you've gained nothing.  That said I do most of my practice with software chess.com tactics trainer and a couple other sites.  As far as wondering if you'd see it over the board, if you practice enough you'll get the sense when a position has opportunity and catch many things that may surprise you.

my opinion

!) not that instructive.  but.. reassuring

2)This is good, but its a sign your Not thinking deeply enough about the puzzles. nevertheless it happens and isn't bad

3)well, thats Learning!  you got the right answer- do you understand it?  if not your to situation 5/6.  Guessing does nothing. on the other hand, if it was just difficult- some tactics are....

4)the most instructive in your list.  make sure your redo the puzzle in the near future

5)effort is good. if you eventually think yuo understand it; about as good as #3

6) the problem is beyond you, probably uninstructive.

sometimes I go for depth and calculation; other times, many simpler problems ("mining salt").  but generally, if you doing simple stuff make it a speed thing- if your going for complexity- Give yourself time and Really look deeply.

In my books I use a system where I make a small mark by the puzzle.

n = I failed to find the first move
1 = I found the first move only
~ = I found more than the first move, but not all of it
U = I saw the whole solution and at least the first few move(s) of the variations.

Oh, and when I solve them, I stare at the diagram, then when I'm completely done with a line, I write it down. That way I know what I missed and can't tell myself "oh, I saw that"

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When I open a tactics book, I usually do puzzles with a few U marks. If I got them right a few times, it's an easy warm up. Then I either do new puzzles (no marks) or puzzles I've failed one way or another.

If a puzzle is like #6, it's really annoying and I find it tedious, but I'll put it in a chess engine and explore some variations. If the variations are not very concrete, then I find these the least instructive. But other than these, the goal is to have solve them all correctly a few times.

Puzzles that are particularly interesting to me I'll write their reference number or page on the inside cover of the book.

It's also useful to think about the mechanics or geometry of a puzzle. Even something simple like as you read this, without a board, when a queen gives check to a king on an adjacent square, can you imagine the pattern of the king's only two escape squares? For both a diagonal check and orthogonal check?

When you threaten mate with a piece like a rook, can you list the types of moves that allow escape? (capturing one of the mating pieces, defending the mating square, blocking a line of attack, creating an escape square)

Whenever you can consciously add little ideas or pattern like this, it will help you solve more difficult problems later. You may also want to save similar puzzles. Like sacrifices on e6, g6, f7, g7, or h7 and look for common themes. (You could probably also good this e.g. "h7 sacrifices" heh.)

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Anyway, to sum it up:

1) Difficult puzzles are good, but not too difficult
2) Review puzzles
3) Think about patterns and geometry afterwards, even if they're simple. 

The answer is, you need to practice calculating, as deep as you can go without moving pieces.  Try solving difficult puzzles from a book (not timed on tactics trainer) 

Try tactics from - 

Chess Combinations - World Champions Vol. 1 & 2 

or something.  Or just pick up some games and advance forward some moves and try to calculate and plan as deep as you can go.  

This can be very good calculation training.

But, if your goal for that training session is tactics, it's better to give up after maybe 10 minutes or so. For tactics you want to learn new patterns and ideas, so ideally you'll see at least a few per session.

I agree with mjh1991, I think starting out it's ok to go quickly through tactics to see many ideas and patterns. To really improve however, at least for some slower time control chess, then spending many minutes even up to an hour is good and probably required for many tactics.  My only issue is the time I spent doing these difficult puzzles with many variations. It can be hard to stay focused, at least for me, because I want instant improvement. Sadly it doesn't work that way. I've looked at some Dvoretsky books and then realized how bad I was at chess :(. I both enjoy and hate looking through those books because they can be incredibly beneficial but man do they give me a headache and make me reevaluate my whole chess playing style. Anyway, I would say if you have the time, go through those difficult puzzles every now and then as you will see many ideas that can improve your game as opposed to the simple 1-2 move tactics.