Yes, of course. You just need to be knowledgeable in some field of study and interested in sharing it with others. I also ask everyone to fill out a form [she holds one out to her] so I know what to put in the course catalog.
It's also good if you can keep an attendance record and some notes on the classes themselves partially so someone else can take over more seamlessly if needed and partially so new students can have something to review since there are always new people arriving.