Press the ALT key to hold your character's head in place, as it will always look in the direction your camera is set in normal camera mode.
F1, F2, F3, and F4 control the cameras.
F1 for first person view,
F2 for normal view,
F3 for Spy-camera, as everyone calls it, in which you can move freely without anyone seeing.
34 for Run-cam, which is barely used.