While we might want to streamline our action and cut out unnecessary toing and froing there are parts that require description.
I once read a book [Title redacted for protection of the not-so-innocent] where there was a big build up to the character breaking through a magic door, there was a lot about how difficult would be to get through, how it would take someone else a long time if they managed to get through it at all, this was the door of doors and so… he did it in two seconds. Um… How? I was thinking. If we build up a problem we need to tell the reader how the character solves it. We could have them planning it before, describing it as they do it, or after the fact. But if we build up the challenge and then just say ‘well, I did it easily’ it’s anticlimactic and so disappointing the reader might stop reading. I did, if you’re wondering, but in fairness the writer pulled the same trick more than once.
Once again we come back to the question of: Do we need to know this here? And while we might not need to know that they crossed a room we might need to know what they did when they got there.
As you might’ve noticed from my description of the nameless book it’s not enough to know that the character outsmarted the antagonist we need to know how they did it. In showing how, or even telling how, we show the reader that the character is as smart as we claim, rather than simply making implying ‘I said they are so they are’. If we do this then it acts more like a plot hole we couldn’t fix, it implies that we couldn’t fix so glossed over. In first-person it can also have the effect of making a character appear incredibly arrogant, ‘I could tell you how I did it but I won’t because I’m too clever for you.’
This principle doesn’t only apply to outsmarting the antagonist there are other smaller things. Perhaps a character has a particular ritual locking their car at some point and another character comments on it; perhaps they lock it, check it, unlock, relock and check it again. Not uncommon but we’d need to mention this at least once before another character drew attention to it otherwise it comes out of the blue and the reader may wonder why it was never mentioned before. We wouldn’t have to mention it every time and a passing sentence to mention it may be enough to establish the habit. Details like these can imply things about our characters and if it is never mentioned unless another character says something instead of implying it can simply be frustrating. Think of characters like Poirot who are made up of these little habits and are more interesting for it. We can even build these habits up so a reader can infer what the character is thinking by what they are doing, whether it’s a nervous finger tap or tugging at the cuffs of their sleeves.
During the first draft we might not even notice these things ourselves but we might put up on them during edits and be able to expand on them to give our characters’ life like behaviours. As I keep saying it doesn’t all have to be in a first draft because a first draft is just us working out how the story goes.