As a photographer for over 30 years, I've noticed when people show me their photos, one of the mistakes amateur photographers make far too often is to shoot people or portrait images taken with a wide angle lens.
Today with the abundance of zoom lenses it is easier to zoom to wide rather than backing up with the camera. But the consequences of zooming wide on a people picture is distortion. The head becomes big out of proportion with the rest of the body. Or, if an arm or some part of the body is closer to the camera than the main part of the body, that arm or part of the body looks huge and out of proportion with the rest of the body. The answer to not letting that happen is to shoot with a more normal focal length lens. In other words, don't zoom to fill the frame, just back up a little and leave the lens set for the normal or telephoto part of your zoom.
You also gain by shooting on the more telephoto setting on your lens as you will include far less background in your photos. And, if you are doing a portrait why would you want to include all the background that is visible. Make the subject (portrait) the center of interest, not the room or location you are shooting in the subject with a person standing in the middle of the location.
When you pick up a fashion magazine ie. Glamour, Vogue, Cosmopolitan, W, notice the perspective of the pictures, the photographer when shooting a full length shot to show the outfit the model is wearing, bends down to shoot at waist or knee level. The photo makes the model look better and no distortion. Want to see bad photos pick up a People or Us magazine. When those photographers shoot the stars on the red carpet or almost anywhere they are shooting wide angle and are far too tall or high for a full length shot. But, that is the way they do it. Next time you are in the check out lane of your grocery store or in the drugstore, compare the images in a fashion magazine compared to the People or Us magazine.
You will begin to understand perspective and distortion.
It is the little things and the attention to detail that make a photographer a great photographer and not just a snapshot shooter.