Lips are DEFINITELY the worst thing about drawing profiles. Lips and the chin. Hope my tips are clear. ""orz that goldfish thing is definitely not clear

I don't normally draw the diagonal, but it's a good check if you want to see if you're on track with your profile. The chin and the nose should touch the diagonal, but the lips don't have to (depends on the character? idk. ;u;)

If you're having trouble with profiles, it helps to look at tons of different artists' ways of drawing the lips and chin. Some people draw more rounded lips, some people draw pointier features... figure out what kind of profiles you like and dislike. It helps you get a handle on how drawing the lips and chin is supposed to look.