Subwoofer thoughts from a newbie...

I have been noticing from people I know that use a subwoofer that a subwoofer seems to get used in the wrong way(or different way). It seems to me that a subwoofer should be used to capture the frequencies that the satelites or mains don't get. That is the way my subwoofer is set up, but it seems people use subwoofers to punch up frequencies handled by the mains and in incense, the subwoofer are duplicating frequencies. Am I using my sub wrong?

Also, I have placed my subwoofer right in the middle of my mains, against the back wall, and that goes against what I hear about placing it in the corner. The two mains are focused to such a degree that it sounds like everything is coming from the center subwoofer and then out of nowhere something kicks in from the far left or far right, especially with classical music. I may be doing it wrong, but it works ok on my so-so system.

I sometimes turn off the subwoofer and honestly, most of the music that I listen to doesn't need a subwoofer. What the subwoofer does for me is add dynamics here and there throughout the music I listen to when the sub is on. I listen to some rock and when it thunders, the sub kicks on. That sort of thing.

What about others?