Really, all you need to do is align the speakers tweaters to a point in the room you define as the 'sweat spot'. Using a laser is great, you would need to attatch it to the front of the speaker baffle and make sure it's level and plumb. Otherwise, a good guess is normally ok for 'regular' installs. But one thing for sure is, delay plays a large part in the imaging of the system. Make sure you use the feature in your reciver to delay the sound from the necessary speakers to have it arrive at the same time (to your ears)

Multiple speakers are definatly not a great idea as Larry mentioned, they create a lobing in the coverage pattern of the speakers and I've seen it so bad that the sound was actually 10 db lower in level for someone sitting only 2 feet off axis of the speaker. (that's twice as soft!)