The best free software is probably Hugin
. Good program, with a lot of good tutorials
For the photographs - manual focus, manual exposure, identical white balance. This is to make sure that images can be stitched to each other. Make sure that there is significant overlap between them. Get the photographer to use a tripod, and ideally one with a nodal point adapter (so that the camera doesn't revolve around its base, but around the nodal point of the lens). Also make sure that there aren't too many moving things in the picture between shots, otherwise they may appear multiple times.
Further instructions partly depend on the kind of panorama you want to do.