A strong opening to a story is able to hook the reader and keep them engaged. Make sure that what you're writing engages you too, and hopefully, should be immersive for everyone else!
Have well-developed characters in your story. Think about what motivates them, what their strengths and weaknesses are. Their backstory, who they are and what they do. What do they bring to the story?
Outline the structure and overall plot to get a better idea of what you want to write. This helps you to avoid writer's block, and be engaged in finishing your projects, and you can always refine your story while writing!