Here are some personal tips I can offer to fellow aspiring writers for your next best fiction stories. There's no particular numbering in the points, so you can go through the process randomly.
Visualize your character
Here's your gem. A leading character should have a strong voice that attract readers to the story. You can tweak him/her/it around, figuring out how exactly who the character really is. Do your homework to understand the strengths and weaknesses the character has. Perhaps the best way to go through is by asking "if I put this as an obstacle, how would the main character react?" Focus on building active voice instead of passive.
Imagine different scenes
Call it daydreaming, but the most fun part for me is to imagine different scenes of the story. Here's your chance to listen to the character's voice. Act like a director and retake the scenes to enhance the flow. Make sure that each scene intrigue your readers to flip the pages. If you're writing a novel, also consider foreshadowing: the technique to give hints for the future outcome in the story.
To make it simple, think of an essential scene, the 'Must Have', the big revelation that changes everything. What was the setting? Who speaks to whom? What was the reaction? What are they fighting about? Then work your way back through to foreshadow it in broken pieces. For example, the major scene is about Character A knowing her mother still alive in a hospital. The elements are: the hospital, someone's in a comma, Character A's lost mother, flower sent to the room. You can insert them in different scenes along the story.
Start plotting or building your story
This is the more detailed task. Now, for a novel (more than 40,000 words) you need to break down your story into parts. Do consider K.M. Weiland's "5 Secrets of Story Structure". It explains the different points of a story, including the Hook, Inciting Event, 1st Plot Point, 1st Pinch Point, Midpoint, 2nd Pinch Point, 3rd Pinch Point, Climax Begin, and Climatic Moment.
Other stories may be in different lengths: short story (less than 7,500 words), novelette (7,500 - 17,500 words), novella (17,500 - 40,000 words). The shorter the fiction is, the more important you need to focus on a certain issue to grab reader's attention. A short story is like a kiss in the dark from a stranger, Stephen King said.
Explore the theme
You need to deep dive into the story to get to the theme. But once you find it, it will be a revelation that you can use it in many story layers. Consider a story as a house. Your plot and structure built the house, with characters living inside the house, and scenes in each of the rooms. Themes then played the role of decorations that unified the whole story together. Once you know your theme, you will have the one thread line of the story. Most of the time, you'd have more than one theme. It could be useful to highlight them as a punch somewhere in your story.
Describe the setting
Whether it's a futuristic, historical, or contemporary fiction, setting brings familiarity to readers. It is the tool writers use to create their universe. In fact, our greatest imagination might lie beneath the very setting we develop. The only way you can invite a reader to your universe, is through good setting. Pay attention to details to create resemblance to the real world: suggesting that the fiction could possibly happen.