What are the best methods of dissecting the human tongue from a cadaver?

First, you need to thoroughly familiarize yourself with the anatomy of the tongue. You should also study the oral cavity and the throat, as your dissection will progress into these areas. For your study I would suggest these textbooks:

1. Clinically Oriented Anatomy, 4th Ed., Keith L. Moore and Arthur Dalley, Lippincott Williams and Wilkins, 1999.
2. Hollinshead’s Textbook of Anatomy, 5th Ed., Cornellius Rosse and Penelope Gaddum-Rosse, Lippincott Williams and Wilkins, 1997.
3. Color Atlas of Anatomy, 5th Edition., Rohen and Yokochi, Lippincott Williams and Wilkins, 2002.
4. Atlas of Human Anatomy (paperback w/o CD), 3rd Ed., F. Icon Learning Systems, 2003.
5. Grant’s Dissector, 12th Ed.., Eberhardt K. Sauerland, Lippincott Williams and Wilkins, 1999.

Then, I would follow the dissector. You might need to adapt (i.e. a wide and long incision carried around and deep to the tongue yield excess tissue, but should keep the entirety of the tongue in place).

You might have a problem with staining secondary to use of formaldehyde (i.e., this might lead to excessive florescence). I suggest an excessive number of washes in 0.1 M PBS to help with this issue. Then, you may use cryostat to cut sections of tissue for staining; 8*10 microns in thickness). It would even be better if you could obtain a "fresh" cadaver tongue. If this presents difficulty, animal tissue (pig or bovine) might be useful. You could then fix/embed the tissue (i.e., paraffin; paraformaldehyde; etc.).

A variety of stains and staining methods are possible. Many of these are found in Histopathologic Technic and Practical Histochemistry. Affinity BioReagents makes a variety of antibodies in nerves. Thus, immunohistochemistry may be an appropriate approach.