Find a subject in front of a background with depth. Take a close viewpoint and zoom in; you’ll need to be aware of the minimum focusing distance of your lens. Focus on the subject and take a single shot. Then, without changing the focal length, set the focus to infinity and take a second shot.
The closer you are to the subject, the shallower the depth of field; the further from the subject, the deeper the depth of field. That’s why macro shots taken from very close viewpoints have extremely shallow depth of field, and if you set the focus at infinity everything beyond a certain distance will be in focus.
As you review the two shots, how does the point of focus structure the composition? With a shallow depth of field the point of focus naturally draws the eye, which goes first of all to the part of the image that’s sharp. It generally feels more comfortable if the point of focus is in the foreground, although there’s nothing wrong with placing the point of focus in the background.
ISO 400, 70mm, F4.5, 1/60 second, viewpoint focused on the numbers on the gate.
ISO 400, 70mm, F4.5, 1/60 second. Viewpoint focused on infinity.