Give me the prize!
I've always said; "In a properly set-up environment, you should be able to close your eyes and point out the subwoofer. You should just feel the lovely bass all around you."
Proper Placement of a subwoofer is THE largest single thing you can do to achieve a great bass response for a number of reasons. First, and foremost; all subwoofers are different. A front-firing sub will react differently than a down-firing one, and the port size and location are almost never the same on different brands or sizes of subs.
Next, I believe a proper subwoofer cable is important as well, but perhaps (after looking at the subwoofer poll results, and really thinking it through) maybe not second out of those options (definitely third though!).
Having to answer again I would choose the Auto EQ setting, as most good receivers do have either microphone or manual calibration available, which is easy and the first thing you should do when setting up a receiver. Not only will your bass be right-on ... but even if you've positioned something improperly, this will often correct it, or you will recognize it being off by the results of the setup; and change it.