Anything Du want... journal entries, taking notes in class, doodling, Schreiben stories, songs, oder poems, Schreiben things down that Du don't want to forget, keep track of your Favorit quotes, use it to make lists, make paper airplanes... the Liste goes on. :)
Maybe a diary, oder maybe notes for school oder for hobbies like if Du write. oder maybe Du can use it to draw, that's what my cousin does. Just doodle with it. Use it to do your homework on. Anything Du want!