There’s no one right way to write your story. Complete pantsing is a totally effective way of writing (don’t let anyone tell you otherwise!!), but if you want more structure or clarity, here are some ideas!
Outline After Finishing. After discovery-writing a first draft, writing an outline based on your draft can be really helpful while revising. I find that it clarifies a lot of plot points that grew naturally while writing. Story Grid, created by Shawn Coyne, is a way to express the change in your story. Or you can summarize scenes on index cards and move them around to create a visual timeline. (And you can color-coordinate them, which is exciting!) Tables and timelines can help to see what each scene gives to the story, the overall progression of the story, and which scenes need to be cut (I’m sorry).
Draft Zero. Another idea I’ve heard is to write a really messy first draft, skipping over a lot of description, dialogue, and even scenes and noting them in brackets instead, and then treating it as an outline and either rewriting it or filling in what you wrote. (So you’re basically discovery-writing your outline.)
Archetypes. Again, there is no right story structure, but archetypes that happen to fit your story can give clarity on plot points instead of having it float around in your head like mine usually do. Two very common ones that I like are the Hero’s Journey and the Three-Act Structure. The Hero’s Journey (also known as the Monomyth) is most common in fantasy, but it can fit into any genre. Usually a Hero’s Journey arc starts with a character in their ordinary life, after which something brings them into an unknown world or situation; then they face trials and some sort of death and rebirth; and then (usually) they finally return to their old life changed. Within that, there are a lot more common details — here’s the Wikipedia article. Regardless of the type of story you’re writing, elements of the Hero’s Journey can help to clarify what different events are doing for your story. A looser model is the Three-Act Structure. Act one: Introduce the characters and problem. Act two: Make everything worse. Act three: Have them solve the problem. And here are some more archetypes. If you don’t find archetypes that fit, you can also define these basic plot points: Inciting incident (what causes the plot to start happening), rising action (foreshadowing, tension, and everything getting worse), climax (the culmination of the plot, in which the evil is defeated), and denouement (resolution and wrapping up loose ends). I also like the idea of expressing plot in terms of connection and disconnection rather than conflict.
The Bookend Method. The Bookend Method is planning the beginning and end, which leaves the middle more open to new ideas as you outline or write, while having a concrete beginning and end to keep you on track.
The Snowflake Method, created by Randy Ingermanson. The Snowflake Method begins with a one-line summary and works outward, creating more and more detailed outlines until you have most of a draft.
Outlining Backward. Some people find it helpful to start with the end and trace cause and effect back to the beginning.
Starting at the Low Point. Some people also begin outlining at the character’s low point (or the death and revival in the Hero’s Journey), or another turning-point scene that feels like the heart of the story. That can make it easier to stay true to the story as you move outward from there.
There are so many more methods out in the world — please comment with your favorite! — but I hope this gave you some ideas. Happy outlining!