Generally, you want the surrounds on either side of your listening position in a 5.1 setup. As far as the sub goes, placing it in the corner will create more bass but possibly make it sound boomy... I would take a look at this article Crawling for bass and this article Home theater layout. Also, I would take a look at the newsletter section of the website... there are some really great articles there.

Denon 5803 Denon 3910 Axiom M80ti's, QS8's VP150, EP500's (7.2)