What is the surest way of determing whether a material is a magnet or not?

To know whether a material is a magnet or not you will need to first know the cardinal directions (using a magnetic compass). Once you know which are the north and south directions, suspend the material freely by tieing it with a string, or by floating it in a bucket of water. Allow the material to settle and notice which directions does it point. If it points towards the north-south directions, then it is a magnet.

There is another method of identifying whether a material is a magnet or not. For this method, you will need a bar magnet with known poles. Firstly bring the north pole near one end of the material. If the magnet doesn't attract it, the material is not a magnet. If repulsion occurs, then the material is surely a magnet. But if attraction occurs, bring the south pole of the bar magnet near the same end of the material. If attraction occurs, then the material is not a magnet, whereas if repulsion occurs, the material is a magnet.