Common Writing Advice (or Rules)

So I thought it'd be fun to gather together the combined knowledge of the group.

I'm curious to hear what everyone has heard as the most common writing advice (or rules) they've been told over the years.
These may be accurate or not.

Please only list the advice/rule itself. Don't try to reason it out or explain it. Just list it.
Perhaps once this thread gets going, we can create threads to tear apart each of the piece of advice/rules.

Get into the action quickly. Don't create large blocks of text. Write for an 8th grade level. Write to a length that suits your genre. Show dont tell. Avoid adverbs, especially those ending in -ly. Don't use worn out cliches or expressions. Show diversity in your characters. Avoid cultural appropriation, and get a sensitivity reader to review your draft.

Write something, even if it's stupid. You can always edit stupid. (Comma optional.)

Apologies in advance. As a copy editor, this is one of several hot-button issues for me.

(Mounts soapbox.)

>> I love cooking grandma and pets. | Don't be a psycho--use commas.

>> What are you nuts? | Here, a comma is required, however it's placement is a matter of style. (This is actually considered polite conversation in New Jersey, bu the way.)

Thank you for your time and attention.

(Dismounts soapbox, retrieves same, and strolls out of the park without uttering another word.

Edited to add: I was unaware that a pair of lesser-than characters prevents the display of anything that ensues, ergo, my comments were omitted.

This reminds me that one should never be one's own editor. Yeah, my bad.

BIS (Butt In Seat) and write every day (James Patterson). Write first, edit later.