First, you need to have a good story idea. This is the foundation of a visual novel. Then, create the characters, design their appearances and personalities. Next, you can start writing the script, including dialogues and plot development. For the visual part, you can draw the backgrounds and character sprites yourself if you have the skills, or you can hire an artist. Also, choose a suitable game engine like Ren'Py which is popular for visual novels. Finally, add music and sound effects to enhance the atmosphere.