Hi Steven.
If your camera is oriented vertically, and you shift the maximum amount (11.5mm) both left and right, you'll only have a small sliver of overlap between two images. That sliver of overlap probably won't be enough to keep the stiching software happy, so you probably need to also do a center shot (three shots total). Likewise if your camera is in landscape orientation and you shift the maximum up and down, you'll need to do three shots. If you shift less than the maximum amount (maybe only 8 or 9 mm), then you can probably get by with two shots.
If you are in landscape mode, and shifting left and right, or in vertical orientation, and shifting up and down, then you can get by with only two shots, since even at maximum shift, you still have considerable overlap between two shots.
A few additional things to keep in mind:
First, shoot in manual exposure mode when shifting. The AE meter is badly fooled when the lens is shifted. If you rely on auto-exposure, shifted images come out extremely dark. This is a metering issue, not the result of how much light hits the sensor when shifted. For example, the manual exposure you use when shooting an unshifted image, is also the correct exposure to use for the shifted case.
Second, if you are oriented in landscape mode, and want to create a panorama by shifting left and right, be advised that you'll get pretty bad vignetting if you shift more than 8mm. If you are in landscape mode and shift up and down (or in vertical orientation and shifting left and right), you can safely shift by the max amount without any vignetting.
Third, if you have close foreground elements, you'll get parallax effects if you shift without moving the body. In other words, if you have close foreground elements, you need to keep the front lens element positioned in the same location while you shift the body. Since the lens doesn't have it's own tripod foot, you'll have to first shift the lens, and then slide the body in it's tripod mount by the same amount in the opposite direction. Hope this last part makes sense. If not, let me know and I'll try to be a little more clear.
I have the 24 PC-E, and it's an excellent lens. I use if mostly for shifts, very seldom for tilts (even tho I'm a landscape shooter). There are some real downsides to tilting that I've never seen mentioned in discussions of tilt-shit lenses, but I've already babbled on long enough.