1. Problems involving threats on a square instead of threats against a piece.
Forking a knight and a rook, A threat involving just pieces, for example I rarely miss. But if the threat is to made against a square, I rarely get it right. Forking a knight and the g7 square for example (i.e. if my queen was allowed on the g7 square on the next move, mate will unavoidably follow)
Actually, it goes simpler. Even if there isn't a double-attack, even if the tactic just involves attacking a square - i do not see them.
For example, in this position
Hmmm...I looked and I looked and couldn't understand the motif or find the key move(*). I thought there wasn't any tactic and it was all a cruel joke. I just gave up and in the end and just moved randomly.
I can see where being proficient with such a motif can helpful. Threatening a square is a 'subtler' form of tactic harder to see than your regular run of the mill pin or fork. Well, harder for me anyway.
2. Knight fork that need multiple hops.
I see the fork if the fork just requires me to move my knight once, and then the fork is there already. But a tactic that involves me first moving my knight to an initial square, and then on the next move then and only then will the fork materialize - this is hard for me to see.
Something like this:
Huh!?Its too bad I cant force chesstempo to serve me tactics having these two themes only. I am forced to wait for my turn, so to speak.
Anyway, for the next month or so, I'll be sharpening this area and holding off on learning strategy for the moment. The concepts I just learned from Nimzowitzch takes time to percolate and sink into practical play anyway. There really isn't any need to rush and finish off 'My System' during the weekend. Heck, Mr. Nimzo thought over the blockade for years before he was able to synthesize and make the system into a coherent whole. I reckon the book should be studied for a year slowly.
Some books are to be tasted, others swallowed, and some few to be chewed and digested.
Sir Francis bacon
So i need to properly digest the book, and only then will I deem myself ready.
Ready for what?
Why to conquer the world and dominate all the chess world of course. I
'll start by defeating that kid who won the Nanjing tournament. Heard he's pretty good.
I'll show em.. I'll show em all!!! Gyahahahaha!! :Lightning crackles in the background:
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(*) The correct answer was Re2 - Threatening mate on the square a2 on the next move.
An FM gave me good advice once - when looking for tactical shots, imagine that you have "super-pieces" that can jump to any square immediately (just for this next move). For example, in the first diagram, super-rook to a2 is mate.
Once you've identified those possibilities, then you can look for ways to make them happen (over the course of multiple moves), often by means of intermediate forcing moves.