Despite how it may look, the best panoramics are constructed with the camera tilted vertically - not horizontally. So tip your camera over on the tripod head. Then take the first photograph, and keeping an eye on where the right hand edge of your viewfinder finishes, move your camera around so that the feature that was up against the right hand edge is now about a third of the frame away from the left hand edge of the frame.
By having your camera on a tripod you should have ensured that the camera hasn't moved up or down at all, just left to right. You need to have your camera on manual exposure as well as manual white balance so that all the pictures match up. Although it doesn't matter if your shutter speeds change it's really important that your aperture doesn't. If you use different apertures from shot to shot your depth-of-field will be all wacky. It's also best to leave your camera on manual focus as well.
In terms of focal length, panoramics are pretty hard to make out of extreme wide-angle lenses. Better to start with something around 50mm and move toward the telephoto end from there to prevent distortion.
Then when you've captured your sequence of shots, time to bring them in to your favourite panorama stitching programme and let the computer do its magic. This shot was taken in the beautiful far norther city of Townsville. Taken off the roof of the Gold Coast International Hotel looking towards Castle Hill. The focal length of the lens was 70mm and it was set at f16.