When I started photography again, with a digital SLR, I discovered the photomerge software and started to give it a go. I read a few articles online and stuck to the 'rule' - use the equivalent of a 'standard' 50mm lens to avoid distortion. After all, taken to its logical conclusion, you wouldn't make a panorama with an extreme wide-angle lens (a fish-eye) because you'd never be able to stitch them together, so there must be something of this nature on a 'normal' wide-angle lens (like the equivalent of 24-28mm). You'd need a much higher number of telephoto shots to do the same job, and they have a distortion of their own, but I don't think you will get any problems.
Of course, experimentation is so easy with a dSLR - so I'm starting to try out different focal lengths. Personally, I still find the "50mm" equivalent the best.
Other 'rules' I stick with.....
Use a tripod.
Get your camera's sensor as upright, vertically, as possible for all directions. A tripod with a spirit level is best for this.
Do lots of shots and overlap a lot - it makes it easier for the software to stitch. If your tripod head has markings, use them as accurately as possible.
Take an average light reading - then set up the camera in manual to use the same exposure settings for all shots.