The direction of the magnetic field at a point is the direction of the force that would act on:
a south pole placed at that point
a north pole placed at that point
a piece of iron placed at that point
a piece of copper placed at that point
40 exam-style questions on AQA GCSE Physics 7.1 Permanent and induced magnetism, magnetic forces and fields, covering 7.1.1 Poles of a magnet and 7.1.2 Magnetic fields. Each one has a worked solution and a mark scheme showing where the marks go.