I'm mostly posting this here for my own quick referencing, but perhaps you may find it informative.

So, when do we use dashes? There are several potential places. Many regions have slightly different writing rules; so, if nothing else, consistency is key.

There are actually three kinds of dashes. The hyphen (-), en-dash (–), and the em-dash (—). (Small, medium, and large). I'm only going to focus on the first two.

Using a dash between two words (Hyphen):
Putting dashes between describing words before a noun.

If I translate that into english, when two or more words describe a noun (person, place, or thing), then dashes (and sometimes commas) are often needed to let us know that all the words apply to that noun

example: heavily-armed guards. The dash is needed because our arms aren't heavy, we are talking about the guard.

Another way of thinking about it: the guards were heavily armed. (Which doesn't need a dash because the thing we were describing came first and descriptor came after.)

More examples:

I shook my head at the more-than-slightly-crazy woman. Nicky was more than slightly crazy.

The water was a beautiful, blueish-green color. The color of the water was blueish green, and it was beautiful.

The short, red-haired woman ran into the house. The short woman with red hair ran into the house.

If the noun is two words, then do not include a comma:

Example: The rusty water tank. The water tank was rusty. (It is actually called a water tank).

The yellow school bus. The school bus was yellow.

It can also be used to show interruptions in dialogue:

Example:

"They should be around here-" "Oh, look at the puppies! They are so cute!"

"Hey, Mom. Have you seen my- Oh! When did grandma arrive?"

Also used to connect dates or in scores:

From 2016-2019, we lived in Canada.

The game is 3:1

Putting a dash between two sections of a sentence to join them (En-Dash, although some people use the Em-Dash):
Using a dash in place of other punctuation or for emphasis.

Some books religiously avoid these kinds of dashes, while others have them dropping in every couple of paragraphs. It's personal preference as to how much you use them.

Some books add a space on either side, and some don't. Whichever option you choose, just be consistent. (The space probably originated from the lack of ability to create the longer dashes in some computer programs, like most email drafts or on the Wattpad create page).

For example, you can turn: 'Nicky pulled two items out of her pockets. It was a bottle of dish soap and a can of tomato juice ' into ' 'Nicky pulled two items out of her pockets – dish soap and tomato juice.'

More examples:

There was only one option left – revenge. (We could have also used a colon or period, although this gives it more emphasis.)

I turned to the person on my left – Jennifer – and told her about the giant spider above the door. (We could have used commas or brackets here, although the dashes make it more obvious that it's an additional piece of information not relevant to the rest of the story.)

The house is clean now – so I expect it clean when I get back. (We could have used a comma here, or even deleted 'so' and added a semi-colon. This is to show emphasis).

That is about as in-depth as I plan to go here. For me, remembering to add the dashes between describing words was my main issue. I'm hoping that typing it up will finally ingrain it into my brain. Time shall tell.