Hi Meg,
To me, the easiest way to ID Goshawk is the white eyebrow. When standing, its overall shape is similar to Cooper's, but larger and and stronger. I had seen very large female Cooper's before, almost as large as Goshawk, but I can feel her shape is not as strong as Goshawk.
Red-tailed's shape is a little bit shorter and fatter, and their faces and eyes are different, Goshawk's eyes are sharper. While in flight, the dark mark on the leading edge of the wings is the easy way to ID Red-tailed.
For your reference.
Calvin
North York