The best time to spot (that is, to detect) a hotspot is the very moment it comes into existence. Then make a good use of it right away (if there are no clearly better alternatives, of course). The game has just started, and already Red has been very kind to Blue with his first move. The square (spot) right under the second O is very hot(!).
And what is Blue going to do with this? H1: PIXY (what else?), cashing in an easy 78 points (!). In this case Red might have a very bad rack (presumably too many vowels). But should he really make that word, then 7F/G7: OORIE would have been wiser. Much wiser.
Here is another one, from the same game.
No one can really blame Red here. There are so many points to catch up (Red’s score above is after he made SOILING). Moreover, with endgame closing in (and so is his time limit), he’s got to do something quick. So generally any bingo would be nice here, for that matter.
But there is something about this SOILING. With J and S both still up, the very position of the letter G here is quite inadvisable—since it would make the DLS square nearby real hot. So, without much sweat, Blue answers with O12: JOGS, 60 points.
Please note that being under pressure, finding a second word for a bingo is rarely an easy task (so maybe that’s why Red missed a much safer alternative like J9: ORIGINS).
Both hotspots above have the same motif. Here is a different one, still from the same game.
This time the bag is already empty (and Red has just moved with AHI). Have a good look at row-K. Note that there are two DWS’s available, which mean that if we can manage to use both bonus squares in one single turn, then either DWS will be the hotspot for the other. Or, in a sense, it’s like having a QWS (quadruple word score) bonus square at our disposal. K5: OUTLANDS, 86 points—including the 50-point bonus, since it’s also a bingo.