A number of organizations have prepared guides to doing oral history for
their own purposes. Some of these are useful for anyone doing oral history.
One of these is a guide put together for the History and Museums Division
of the US Marine Corps:
Another good place to start is a set of instructions developed at the Bancroft Library of the University of California at Berkeley:
The same university has an excellent One Minute Guide and Two Minute Guide to oral history:
For a more substantial discussion of oral histories and how to evaluate them see the pages of the Oral History Association, particularly
http://www.dickinson.edu/organizations/oha/EvaluationGuidelines.html#Principles%20and%20Standards
You can also consult published books with information on doing oral histories. Among these:
Thad Sitton, Oral History: a guide for teachers (and others) U. of Texas Press, 1983
Cynthia Stokes: Like It Was: a complete guide to writing oral history, Teachers and Writers Collaborative, 1988
Ronald J. Grele with Studs Terkel, Envelopes of Sound: the art of oral history, Transaction Books, 1985
David D. Kyvig, Nearby History: exploring the past around you, American Association for State and Local History, 1982.