Some quick questions regarding speaker/sub woofer placement...

[Steelmaker]

My tv room is bascially a rectangle (8'x16'). My couch is centered in the room, up against the wall. My TV is of course adjascent to the couch. I'm getting ready to install my home theater and I have a few questions...

1.) Considering my layout, I cannot place my surround speaker behind my couch. I'm guessing my best bet is to place them at each corner of the back wall and aim them down at my couch. Is this my best option?

2.) Is it true that my 2 front speakers should be approximatley the same height as my sitting height and the rear speakers should approximately be the same as my standing height? I've seen people's home theaters where both sets are elevated all the way at the top of each corner of the room.

3.) Where would the best possible place be to have my subwoofer? I've seen some placed beside the tv, some behind the couch, etc. Is there really a right or wrong place?