Honestly I have never seen a F-22 actually flying, and the F-35 only a handful of times. They look so familiar to me I would be hard-pressed to tell them apart.
Good question.
First picture, F-22. Second, F-35. As seen from the bottom.
The more you look at them, the more differences you'll see. But at first glance, the easiest ways are to look at the engine exhaust (F-22 has two, F-35 has one), the wing tips (F-22 wing tips and tail tips are not "squared off", F-35 are), and the engine inlets (F-22 engine inlets are undercut where you can very easily see inside the inlets, F-35 are pointed forward at the outer edges).