Like @lonestranger said, start at the tail when identifying hawks. This tail length and pattern (gray with black stripes) is present in only three North American species, which are the members of Accipiter: Cooper's Hawk, Sharp-shinned Hawk, and Northern Goshawk.
Members of Buteo have tails that don't project as far and tend to be primarily black with white stripes, with most juveniles having white tails with light brown stripes. The adult Red-tailed Hawk is the exception with its bright red tail.
Individuals may exhibit significant variance, but this is a good starting point.