1) Too much exposition can be boring.
If you've got an awesome flaming sword (or a Chekhov’s gun), you're going to want to use it. You won't want to listen to some NPC drone on and on for hours and hours. Yes, information is important and you'll never solve the story's mystery if you don't talk to people or listen to clues, but eventually you'll want that local farmer to shut their yap so that you can start doing some things. Knowledge is great, but if your dialogue seems to be going on for too long, toss your character a task that needs completing, even if it's a simple one.
2) Too much fighting can be exhausting.
Fights are thrilling, but if your character is going from one fight to another to another to another, eventually you'll get battle fatigue (just like your character). You'll want to rest and heal up, maybe go to a hospital. Or maybe you'll just want a quick nap and a sandwich. Either way, action's great and all, but too much of it and you risk tiring everyone out*.
3) Hindsight is 20/20.
Sometimes I'll look back on sessions and think about how I should have done *this* thing instead of what I actually did (I should have asked that question or I should have used that spell). With DND you don't get a second chance, but at least you'll remember next time. Luckily, when it comes to writing you've always got your edits, so go ahead and make mistakes. If someone dies in a first draft, you can always resurrect them later.
4) Practice makes perfect.
When I first started role-playing (which wasn't that long ago), I knew the basics, but there was plenty of room to grow. I wasn't sure which questions to ask or how to maneuver around the world, and I was constantly worried about making mistakes. But throughout multiple gaming sessions, I learned how to use spells and items to my benefit (and to the DM's misfortune), and I grew more in touch with my character and her motivations. Just like writing: the more you do it, the better your skills will get.
5) Character choices don't have to be right or wrong, as long as they're strong.
I've been watching Dimension 20 far too much for my own good lately, but there's a moment in The Unsleeping City episode 7 where there are a lot of powerful character choices coming out and it is amazing. You might not agree with what each person says, but you have to admit that each character's opinion is deeply rooted in an understanding of themselves. When you're writing a character, you want to make sure everything they do is something that fits their character. You can't have a pacifist going out there and killing everyone without a reason for the change.
6) Do something!
In role-playing, the game doesn't progress if your characters don't do something. Sure, the DM can throw obstacles your way, but if they're the one controlling everything, then maybe you should find another game. It can be fun to watch a character get pulled from one moment to the next, but as time goes on you might wonder why we're not following someone who's an active participant**.
And, hey, if you're looking for an adventure about a group of people setting out on a quest, maybe check out my new story: Choose Your Own Adventurer, Campaign 1: Origin Story! The eBook goes live tomorrow!
Choose Your Own Adventurer: because sometimes you can't decide which class to play, so you write a story about a bunch of them.
*One exception is the hallway fight scene from Daredevil Season 1 episode 2 - the character's exhaustion is what makes it so amazing.
**Of course, now I'm wondering if I could write a story like this, because I am naturally stubborn.