Manga artists draw backgrounds by first imagining the scene in their minds. They consider the setting, the light source, and the overall atmosphere. Then, they make a simple outline and gradually build up the details. Sometimes they use special effects or patterns to make the background more interesting.
Well, it depends on the artist's style and the story's mood. Some start with a rough sketch to lay out the basic composition. Then, they add details and choose the appropriate colors. Perspective and depth are crucial, and they might use tools like rulers or digital brushes for precision.