When people get shown a strong move they say "I didn't think of that", so I'm going to take a guess and say that the answer is to think. At the very least I it's something I need to do more. All too often I play just on instinct, or make a move that achieves an immediate goal, without thinking about what kind of situation I expect to arise from it.
It is this attitude that seems to be the problem, according to the chess literature mentioned here passim. Recall the award-winning book "Move First, Think Later".
A famous chess trainer is mentioned elsewhere as remonstrating with his pupils. When he asked why they played a certain move, they invariably began, "Well, I thought..." And he says, "Stop right there! That's the problem."
What it really boils down to is that you need to do the thinking work before the game, not during. Of course, there's much more to it than that. For one thing it's important to do the work in such as way that it becomes part of your intuition rather than just part of your deep memory. Repetition has a lot to do with that, but I think it's Rowson who made the point that the order of doing the work is also important because that determines how the part of your brain that subconsciously makes all the associations sorts out the connections for you. Efficient associations are obviously valuable, but interestingly they don't seem to depend on a naive "fundamentals first" policy. You can dot around studying what you like, so long as you avoid contradicitions (i.e. confusing your brain as what goes where in the associations library). But even that is not the key. The key seems to be doing your study in a way that avoids ego, in two ways. One is called (I think) self-identification - how you see yourself as a chess or go player. You may think of yourself as, say, an aggressive player. That will get you into the bad habit of learning only things that reinforce your self image. This is not only a severe limitation but may be the biggest problem of all. As we can see for ourselves on L19, many weaker players like to mention that they try to play like Shuwa, or whoever. Apparently the same syndrome exists in chess.
The other problem is over-confidence in one's reasoning, especially when it comes to drawing conclusions. Weaker players tend to be much more confident than strong players. The very strongest players actually are very wishy-washy. Time and again the chess writers report (and you can see this on chess sites where kibitzers are allowed, but of course also in go on kgs) that on being shown a new position weak players say things like, "White is winning" but a strong grandmaster will say,"Maybe White has chances". A very strong grandmaster will just say, "Hmmm". Actually this paradigm (which I gather applies to other fields of endeavour) seems to work so well that I suspect it may be how pros assess the grade of players they meet for the first time.
So in summary, you need to be prepared to study a lot, but with humility and open-mindedness, you need to allow your brain to sort out all the associations for itself (the part called "the beast within") and then you need to trust that beast to supply good moves to your intuition. Obviously, in real play you need to think about these moves, but not in the sense of
finding (aka seeing/recognising) them. You need to
verify them, either by calculation or by asking yourself whether there are extraneous factors influencing you, such as time pressure or your place in a tournament (e.g. whether to play for a win or a draw).
Naturally, if you can add to that mix the guidance of a teacher who can make sure that your study avoids contradictions as much as possible, then you will make even more progress. Most of us can't afford a teacher, but perhaps studying the games of a single player - as pros so often recommend - is a proxy way of avoiding contradictions over a long period of study.
At the risk of overegging the pudding, I think it would be wise to add another nugget from the chess experience. Among perennially weaker players it is common for them to learn one significant item, such as a proverb, a formula or a new way of looking at things, and then to experience a surge of improvement. Almost invariably, however, they soon fall back to their old grade. A common response then is to buy more books or more snake oil in the hope of getting another "high". But chess or go proverbs and formulas work no better than drugs.
Depressingly, the best advice for playing good go is a four-letter word ending in k and wrapped up in a two-word phrase:
So, as far as possible, I try just to play the best I can in whatever position I see before me.
)