Jazznut,
If you really want to get precise (i.e. anal) about placing your sub, you should put the sub in your listening position, play some bass-heavy software (or test tones), and crawl around the room until you find the spot where the bass sounds best. That spot will be the ideal place to park the sub. Often this is not at all convenient, so experiment with standard non-obstrusive locations, such as near corners, under the coffee table, next to the couch, etc. You really do need to do a fair bit of experimenting, because even a few inches difference from the wall, for example, can make a huge difference in how a sub sounds in your room.
As far as setup goes, set the crossover all the way up on the sub. In the "speaker selection" menu of the receiver, set your mains and surrounds to "small" (the VP150 can be run as a large speaker, although again, you can experiment). If the Yamaha offers you the choice of specific crossover frequencies like the Outlaw receiver, you might start with 60 Hz for the M22s and 80 Hz for the QS8s, then tweak away.
Use your favorite music to set the proper gain on the sub. You can always turn it up for movies, but chances are you won't unless you have a desire to bathe your brain numb with bass watching action movies.
When you watch movies, I would switch the "audio/video" knob to "video"...this will increase the low-end output to add more impact to LFEs (explosions and rumbles), although it gets irritaing with music. This is also a really easy thing to switch back and forth when you've got the gain *exactly* where you want it for music.
I would actually suggest turning the phase to the 180 degree position, because more often than not the sub will be out of phase with the other speakers. As usual though, experiment while playing your favorite tunes to see what sounds best. The Sound and Vision Tune-Up disc has specific noise signals to set the sub's phase, in addition to its other useful tools.
Good luck!
