Surround set up start with three speakers not including subs. Adding sub on the setup means your sound properties can rich very low frequency that usually the other speakers cannot produce. It is actually simple logic. More speakers mean you get the sounds coming from more directions. That is if you are actually setting at the center of the scene or the source disc, examples: Movies, Multi-channel audio, Concerts are encoded with surround system. You can have as many speakers surrounding you but if your source is not encoded with surround system then you will not get surround sound, unless your equipment can process a VIRTUAL surround, which means it can create a surround sounds on its own from a single channel or two. A discreet signal from the source usually comes labeled on the disc or the cover with DD 5.1, DTS 5.1 Surround 3 etc. Here is a link; you can read more about it. http://en.wikipedia.org/wiki/Surround_sound
Setting up a surround is a preference. Some don’t care much of it and some are very accurate on how they want theirs setup. First, equipment quality usually plays a major part of the sound quality. Second, you need to place the speakers where it is hard to pinpoint where the sound is coming from and the rest is up to you.