That's Tumblr for you!

Just find the power wire and the video cable. Cut the wire, open the side up and take out the recorder. Then take of the video cable.
Unless you're stealing something, then just smash it or stay out of sight.

Somewhere I saw that a $2 can of silly string works great! Just disengage the contents of the can onto said security camera.
I think I saw this on FS.

Wirst off it depends on what type it is like is it a stationary with a hardcover or does it swivel with all its wires hanging out. Of course, dismantling a security camera can also alert to people you are there, so you'd probably just want to stick in the blindspots.

Payday 2 taught me we need to kill the guy in the security room first and then cameras won't give us any trouble

Week, first flash a laser to blind it, then move to the blind spot underneath it, then you can safely dismantle. Just make sure no other camera sees you :)