There are several rules in writing that are rather flexible.

- Don't break the fourth wall
- Don't start sentences with 'But' 'And' or 'It'
- Introduce few characters in the first chapter
- Reduce the use of adverbs
- Avoid 'passive voice' (i.e. was taken)
- Show don't tell

etc. etc.

Many books can break these rules and break them well. But one rule cannot, in my opinion, be overlooked and that's Chekhov's Gun.

Chekhov's Gun states that if a gun on the wall is mentioned in Chapter 2 then by Chapter 5 it MUST go off. That is to say that anything you bring up, ANYTHING you bring up, MUST serve a purpose later on.

If an apple is mentioned in great detail, there'd better be a razor in it.

By employing Chekhov's Gun, an author can keep their writing dynamic and deep. There's less danger of veering off into ramblings that serve no purpose in the over all story.  Should an author ignore Chekhov's Gun, more than likely, the story will lag, bogged down with potentially pretty but ultimately useless utterings that serve no greater purpose than a momentary eye-gasm that's instantly forgotten AT BEST, or drone on and on with no focus AT WORST.

For your first draft, put EVERYTHING in. Ignore each and every rule if you must. Let your thoughts and inhibitions run wild. But once it's time to edit, put on your surgical mask, rubber gloves, and get the axe as you start immediately applying Chekhov's Gun.