I am quite a fan of Common Buzzards and, like many folk these days, can see them from the garden most days of the week. This shot was taken last week and I have posted it as it shows a nice comparison of adult and juvenile structure.
In the picture above, the adult (above left) shows a nicely parallel wing shape, solid dark trailing edge to the flight feathers, evidence of moult in the flight feathers and a broadly based slightly shorter tail. The juvenile (lower right) has a narrower hand so a distinct S-shape to the trailing edge of the wing, no clear dark trailing edge to the wing feathers, no clear evidence of moult (i.e. all flight feathers of a similar age) and a narrower, longer tail. The juvenile has an altogether more harrier-like jizz in this picture.
Some of these details may be clearer in these cropped images. Once again the adult is shown above the juvenile.
These differences are less distinct when birds are moving away from the observer, as shown in this shot. The more distinct trailing edge of the flight feathers in the adult is still obvious in direct comparison.