Well, first of all, you should have a clear plot in mind. Don't start writing without a plan or you might get lost in the middle.
One important thing is to avoid cliche storylines. Try to come up with something unique and fresh. Also, pay attention to the character development. Make your characters interesting and relatable.
To not write comics poorly, you need to study the art of visual storytelling. Understand how to frame panels, use proper pacing, and convey emotions through images. And don't forget to do research on your chosen topic to make it more authentic.