Before you start drawing your comic or manga you will need the following:
you can either write one yourself or work with a professional writer.
you need to envision the general color scheme and theme of your comic or manga. Make a vision board to help you build the world or the atmosphere of your drawings.
you need to first create a design of your characters, what they look like, what they wear, and finally, how do they look different when displaying different emotions. General knowledge in anatomy and body proportions is a great advantage here.