I don't get perspective! Help!?

I've read two books about perspective and I just don't get it. I've practiced with it and it just feels like all the rules are cupped in my hand like water and just leak out. I can't even fathom any form of point perspective when the vanishing point is off the page. I also have no idea how to apply perspective to anything but boxes and cylinders. The figure just doesn't look right when I try to encase it in a box. Any tips or helps I can use to get it? Also, I can only find basic perspective rules like one, two, and three point perspective when I know there are crazy things like fish eye or circle grids.