I work voluntarily at a university radio station. We are a small team of three technicians, but the team changes quite often. I have been there for four years now, which is already quite long as people come and go as they finish their studies. We keep track of everything in a dokuwiki. Often I catch myself not wanting to document stuff, but it is essential for coming technicians to have a place where they can look stuff up. That was the place to learn about how the infrastructure works for me when I was new. The second tool we use is openproject for ticket tracking. We don't delete old tickets, so if a problem comes up again it is likely that there is already a solution for it documented in the ticket system.