Find a scene that has depth. From a fixed position, take a sequence of shots at different focal lengths without changing your viewpoint.
Use the sequence to get a feeling for how the angle of view corresponds to the different focal lengths for your particular camera and lens combination. Which shot in the sequence feels closest to the angle of view of your normal vision?
Does zooming in from a fixed viewpoint change the appearance of things?
With each increase in focal length you become closer to the subject without actually physically moving towards it. You are unable to fit as much of the scene into the frame.