Or: Raptor ID Made Easy Easier.

Let's back up a step: This is a redtail, aka Red-tailed Hawk (Buteo jamaicensis). It is one of the most common, widespread raptors in North America; its breeding range is pretty much all of the lower 48, and much of Canada and Alaska. So if you want to learn to ID hawks, first learn the one you've got the best chance of seeing:

Juvenile Red-tailed Hawk - note the not-red tail. Also, note how far down the tail those wings come.
It's a big bird that's brown on the back and most have various mixes of brown and cream on the front (more on that in a bit). Redtails are part of the Buteo family, soaring hawks that focus mostly on mammals, reptiles and birds on the ground - but they will take birds in flight or anything else they can sink their talons into. Adults have bright rusty red tails, from which the species got its name. Juveniles' tails have alternating bands of light and dark brown. Sometimes it's hard to see the color when you're looking at the back of a perched redtail, because its wings may cover much of the tail (wingtips are roughly at the tail tip).

Adult tail above, juvenile tail below. The adult's tail is more heavily marked than you'd normally see - the bird at the top of the

A few fine details which come in handy for separating other species: Redtails have a dark mark that you can see at the leading edge of the wing when it's flying - a "patagial" mark (because that part of the wing is called the patagium). No other North American hawk has that mark, so if you can see it, you have sealed your ID. Also, juvenile redtails have yellow eyes; adults have brown eyes.
Once you know this common hawk, it's going to make it much easier to identify all the rest.

A pair of adult redtails. This shows how color, size and shape can be affected by angles and lighting. That's why it's important to watch the birds for as long as you can to make sure you're really seeing what you think you're seeing. (Also, note the patagial mark nicely illuminated on the leading edge of the lower bird's wings.)