Show don't tell. At some point, every writer hears it and every writer hates it. It's critical to crafting a story that works, but what exactly does it mean? And more importantly, how do you make sure you're using it correctly in your own work.
Showing is dramatizing, making readers feel in the moment and there with the character as the story unfolds. Telling is hearing about it all secondhand. It's describing the situation, not the story. Kinda like reading a review of The Lion King vs. going to see The Lion King.
One trick I use to show and not tell is to imagine myself acting out whatever it is my characters are doing. If I can do what they do, I'm showing. If not, I'm telling.
"I hate you," I said angrily.You can stand in the room and say "I hate you." But act out "angrily." You can't really. You can act out things that show angrily, but there's nothing about the adverb itself that you can physically do. The only way to show it, is to do something else.
"I hate you," I yelled, kicking the door closed.Now, you can yell and you can kick the door closed. Both show anger and let someone watching you be able to figure out your mood by observing your actions.
Try this one:
I walked slowly across the room.You can do this. Slowly has a physical connotation, so even though it's an adverb and needs walked to complete it, it conveys real actable action. But when you walk slowly across the room, exactly what do you do? Tip toe? Slink? Even though you can walk slowly, there's probably an even better way to describe it.
Thoughts are a little harder, as you can sit there and think, but it's what you think that makes all the difference.
She sighed, realizing she'd left her car keys on her desk.Sighing you can do, but act out someone realizing. Again, you really can't. You're telling that the person is realizing she forgot her keys.
Oh crap. She sighed. The keys were on her desk, right next to the stupid report she also forgot to grab.You can sigh, and you can think "oh crap," and you can also think the internalization that comes after.
Thoughts can be extra tricky, because sometimes it is acceptable to say things like, "I wondered if there was any ice cream in the freezer" or "I realized how stupid I was being." I wish there was a hard and fast rule for judging this, but there's not. It's just something you develop an ear for over time. The rule of thumb I use, is to keep them to a minimum and keep them in the point of view's voice. As long as it feels like the character thinking it, you're usually okay. But as soon as it sounds like the author butting in to explain things, you've fallen into telling.
This trick won't apply to everything, but it's a good foundation for most show don't tell problems.