How do you hatch a shiny Charmander?

You can't catch charmander. You have to receive it as a starter in Red, Green, Blue, FireRed or Leafgreen or get it from the person in Pokemon yellow. Whether or not it's shiny is up to luck. You just have to restart the game over and over (or save right before you pick your Pokemon) and receive the charmander over and over until you get one that's shiny. Chances are really low, though, so good luck.