How Can I Determine the Positive and Negative Sides of a Magnet?

One way to determine the north and south poles of a magnet is to hang the magnet by a light string and allowing it to hover freely and horizontally. The north pole of the magnet points toward Earth's north pole. Placing the magnet on a lightweight platform, such as a piece of foam, and then floating it on a liquid surface, also shows the north pole and south poles based on the directional properties of the magnet.