How Do We Know North from South?
Have you ever wondered, when you are looking in a telescope at a planet, or at an astronomical image of one, which is the north pole and which the south pole?
The best way to wok out "which way is which" is to gently bump the telescope and see which way the planet moves. From that you know how what you are seeing relates to what's in the sky, and from that you can figure out which "side" of the planet, for example Saturn with its rings, is tilted towards Earth.
Whether to call that side "North" or "South" is actually really up to you, but astronomers have decided that "North" is the pole of the planet that is less than 90 degrees from the Earth's orbit's north ecliptic pole, which relates what we see directly to Earth's orientation.
A less Earth-centric definition, and one that still makes sense even if the planet happens to be rotating on its side, is that the North Pole of the planet is such that the planet rotates counter-clockwise when you look down upon it..