Components to Magic, What do you have to do to cast? Options

[Zemiron]

I'm trying to figure out if you have to do anything while casting a spell to cast one, e.g. whisper words of power or gesticulate in some way. From all the flavor stuff I've read (novels and such), this is required, but my friends have never played this way. It doesn't make that much of a difference. I'm just curious if when a mage manabolts somebody, does the mage just stare at the guy and he suddenly starts bleeding out of his nose or does the mage whisper something and/or move his hands in a certain way and the guy falls over. It makes a difference in regards to security cameras and such. Thanks!