My method to stitch:
1) make 2 photos with:
- same manual exposure setting and the same white balance setting (not auto)
- overlapped +/-20 percent
2) duplicate both image files and reserve
3) open left one in PS/PSE then select canvas size, in dialog window place imaage at center left then overall new size to double the original width
4) open right image then drag to empty right hand spot in your canvas, move until happy with position
5) choose box select tool set to 30px feather and select a small section of the overlapped portion, then delete
Re-do if improvement is needed.
Images made LEVEL at a distance with 'normal' focal length setting/lens work best.
Grid lines in finder help composition.
Wide angle, esp. if close require camera rotation on the nodal point.
If you are going to stitch several, Hugin for Mac is free and uses same PTools engine as PTGui, just does not have such a nice G.U.I.
If you do not have PS/PSE the latter is very inexpensive on CD and PSE v8 or older does not 'Phone Home'.
For repro work one needs to set up a system for moving the camera parallel to the subject.