**It doesn't have many steps.**
All you have to do is run forward then jump and press the rag doll button at the same time. And just before you hit the ground, press the first person button. Keep trying until you see an extra set of arms on the character you're controlling in 3rd person. Now go back to first person and your camera moves realistically. By the way, your arms won't show in first person, and when you run your camera moves the direction the characters head moves in 3rd person, and aiming is insanely hard. (It's still worth the pain.) It does take a little practice, but when you master the glitch it's easy. Enjoy, fellow gamers!