Whenever a gun gets pulled out and a cocking noise gets played. No, pulling a pistol out of its holster or bringing a rifle to bear does not automatically cock the weapon. Racking the slide/bolt cocks the weapon. Also, a "clip" is not a "magazine," the two are not interchangeable nor are magazines of infinite capacity.
Movies like Blood Diamond which feature things like press checks and aimed semi-auto fire instead of "CHK-CHK: budda budda budda" AK fire from the hip icing countless dudes do a lot to add to the feel of the movie. If its something like the Matrix, I don't care much, but movies set in the real world would do quite well to pay a firearms enthusiast to ensure realism. Another good example is Heat - the weapons were very well done and were showcased in an excellent fashion. Tons of FN FAL and FNC porn, too.