user5855: In even the most quiet-looking position there might be a tactical bolt of the blue, but consider a game might last 50+ moves, and your time and your concentration are limited resources. Thus it is not feasible to do like a computer and calculate each and any position many moves forward to be safe. So, to use your resources effectively,
What are the objective criteria which suggest the position needs immediate tactical attention?

user17425: I suggest "Tune Your Chess Tactics Antenna" - know when (and where!) to look for winning combination.  It aims to precisely improve knowing when to take more time for specific tactics.  Also covers thought process generally.
The chapters get a good sense of what to look for

King Position
Unprotected Pieces
Alignment
Knight fork distance
Trapped pieces
Crucial Defender / Overloaded Defender
Impotent Defense / defense Too far away


user4418: Every position after the first few moves of the opening requires a certain minimum level of tactical attention. Even in a quiet position the first questions you should ask your self after your opponent has moved are:

"What is my opponent now threatening?" and
"What is my opponent trying to achieve with that last move?"

These questions can have both tactical and positional answers and they can have more than one answer. Asking these questions is what Nimzowitsch called "prophylaxis" and it is what separates bad players from good players.
Positions where there is tension, where captures on both sides are possible always require some calculation if only to decide whether it is a good idea to resolve the tension. It is particularly important to keep an eye out for tricky little zwischenzugs and by both sides. Again, both material and positional factors need to be considered in evaluating the position after the dust of exchanges has settled.

5855: <p>In even the most quiet-looking position there might be a tactical bolt of the blue, but consider a game might last 50+ moves, and your time and your concentration are limited resources. Thus it is not feasible to do like a computer and calculate each and any position many moves forward to be safe. So, to use your resources effectively,</p>
<p><em>What are the objective criteria which suggest the position needs immediate tactical attention?</em></p>
 17425: <p>I suggest &quot;Tune Your Chess Tactics Antenna&quot; - know when (and where!) to look for winning combination.  It aims to precisely improve knowing when to take more time for specific tactics.  Also covers thought process generally.</p>
<p>The chapters get a good sense of what to look for</p>
<ul>
<li>King Position</li>
<li>Unprotected Pieces</li>
<li>Alignment</li>
<li>Knight fork distance</li>
<li>Trapped pieces</li>
<li>Crucial Defender / Overloaded Defender</li>
<li>Impotent Defense / defense Too far away</li>
</ul>
 4418: <p>Every position after the first few moves of the opening requires a certain minimum level of tactical attention. Even in a quiet position the first questions you should ask your self after your opponent has moved are:</p>
<ul>
<li>&quot;What is my opponent now threatening?&quot; and</li>
<li>&quot;What is my opponent trying to achieve with that last move?&quot;</li>
</ul>
<p>These questions can have both tactical and positional answers and they can have more than one answer. Asking these questions is what Nimzowitsch called &quot;prophylaxis&quot; and it is what separates bad players from good players.</p>
<p>Positions where there is tension, where captures on both sides are possible always require some calculation if only to decide whether it is a good idea to resolve the tension. It is particularly important to keep an eye out for tricky little zwischenzugs and by both sides. Again, both material and positional factors need to be considered in evaluating the position after the dust of exchanges has settled.</p>
