By personal example. If possible, use film and print wet. Show your work, even if it is on the local cafe wall. Teach others.

I run the teaching darkroom for a university's art department. I volunteered as a darkroom assistant there for 12 years before becoming the paid tech for the past 20 years. In one way or another and to various degrees, I interact with 125 students every semester. I check out, and demonstrate the use, of small, medium and 4x5 cameras. Students come to me for ways to get their ideas onto film and/or onto photo paper -- but I don't teach a class: I have a bachelors degree -- in science! (Actually a BS in Natural Resources Management.) There are another 25 students per semester taking a digital class, but I only see them when they sneak down the hall and use the darkroom. (okay, they don't have to sneak -- they get darkroom privileges too.)

I have taught younger kids film camera and darkroom work at summer art programs (4th grade thru high school) -- including making their own pinhole cameras, exposing onto litho film and making cyanotypes and silver gelatin prints. I give demos at grade schools and have one scheduled for the high school. Three different classes, I think. All digital classes, but the teacher and I want to give the students a look on the silver side (along with some platinum and carbon). I'll have the 8x10 set up.

If there is no longer film available, then I will learn how to make my own dry plates. Or perhaps when I am 70, retired and my three boys are out of the house. Whatever comes first. Until then, I will happily buy film and be satisfied with making my own print material (Carbon printing). Though in all honesty, by the time (if ever) film and photo paper are no longer available, I could probably still make new carbon prints from old-but-not-yet-printed negs until I could no longer stand at a darkroom sink. What a backlog!