The Flow DiagramWEB TUTORIAL - Group Theory
You will need to familiarise yourself with this as it is not given in exams, but it will help massively for determining point groups until then.
To use the flow diagram at each step you are asked a question about the symmetry of the molecule. By answering YES/NO this will guide you to the point group.
You will work through the flow diagram in a stepwise fashion for both of the worked examples.