Step One: Find an institution or organization to be the repository for the interviews- it can be a university, a library, a local historical society, or a local of a teachers union. You need to find some place to store the interviews and make them available to the public
Step Two: Get together a small interview team to develop a list of questions as well as release forms which detail the conditions under which the interviews can be used. Many people will want to disguise their identities and you have to develop protocols to assure anonymity. I can send you a sample release formd from the Bronx African American History Project both for people who want to be interviewed under their own names and those who don't..
Step Three: Purchase the equipment needed to record the interviews, which will consist of digital tape recorders and/or digital video cameras ( you will have to decide if, and under what conditions the interviews will be videotaped).
Step Four (optional). Raise funds to get the interviews transcribed
Concluding Comments: The initial investment to get a project like this started is well under a thousand dollars. The hard work is getting a small group of people to design and conduct the interviews and locate an institutional repository for them. I guarantee you will have no problem finding teachers to tell their stories.