What is the most important question to ask yourself when calculating

My point in posting that game was that my opponent operated with direct threats, move after move. Each threat seemed to allow only one reply. But after I found this series of "only" moves, my opponent's position was overextended and collapsed within a handful of further moves.

The original question that I was answering with my advice posted above was "How do I force my opponent to use more time than I'm using"... and forcing moves do NOT accomplish that. If the opponent has only one reasonable move, why would he spend ten minutes calculating it?

The way to make him use up time and get into time trouble is to present him with a series of difficult choices. Not a series of "only" moves.

play moves that are good

That's not a question.

yea it's an answer

Questions that ask for questions can't be answered with an answer

It's an answer in search of a question!

Let us know if you find one.

the most important thing is to play moves that are good, so the extension/question version of my answer would be "what move is good?". 

When your book report is due today but you forgot to read the book:

"The most important thing is that words are made up of letters"

meanwhile your advice was to not play stupid moves

Touché