Conversationally, a bore is a person who tells more than we want to hear. A photo can be just as boring, by showing more than we want to see.
The camera's eye sees everything, tells all. It doesn't have selective vision, like the eye. So we have to help the machine select what we want. We can do this through the lens when taking the picture, or by cropping when printing.
Cropping in the camera can be done by moving closer to the subject, changing to a longer focal-length lens or choosing a different viewpoint. The simplest is just to move in closer.
Too small an image is the chief difference between the pictures of an amateur and a pro. The amateur wants to be sure not to cut off anybody's head, so he moves back just a little further and overcompensates. The pro, on the other hand, is concerned about the exact picture and moves closer. The pro knows the larger the image on the negative, the better print can be made.
Changing to a longer focal length lens, like a tele, will do the same thing as moving closer, but will change some of the picture elements. It changes the perspective by flattening out the picture planes; the depth of sharpness will also be less. These two factors can be an advantage. By flattening the perspective the picture is tighter; and by having a sharp focus on the foreground and letting the background go soft, the composition is simplified.
A different point of view won't make the image larger but it may change the composition so no cropping will be needed. For example, by taking a higher camera position, standing on a chair or ladder, the sky can be eliminated. By choosing a low, looking-up view, a figure can be silhouetted against the sky. Moving to the sides can include foliage to frame the picture or exclude excess greenery.
Cropping the negative can best be done in the darkroom, but if you want to be sure of the result or if you send the photo to a lab to be enlarged, determine the cropping beforehand.
Use two pieces of L-shaped cardboard to use as a trial frame. By moving the pieces closer together or further out, you can eliminate excess picture.
All these methods eliminate unwanted detail, but the best way is to develop selective vision so that you don't need to alter a photo.
Before you snap, ask yourself some questions: What do I want this picture to say? What can I leave out and still make a complete statement? Where is my best camera position?
By answering these questions in advance you won't have to go to the trouble of cropping later. If the picture is of grandmother and you want to emphasize her kindly face -- wrinkles and all -- move in close for a portrait and choose a pleasing eye-level camera position. If, on the other hand, the picture you're about to take is of a group, move back to show them all and try both a vertical and horizontal camera position, to see which one fits.
The tendency is to let the camera do everything. But it doesn't have to be that way, if you tell it what to take -- and what to leave out.