1) Decide you should create a group listserv. Don't ask permission. Add a group of people to it, because you're certain they will appreciate it. You know how valuable this newfangled tool can be.
2) Send the first email to the group, announcing the existence of the listserv. Make this announcement email very, very long -- about 700 words is good -- and bury the technical information about the listserv (how to unsubscribe, for example, or the distinction between replying to individuals and replying to everyone in the group) deep in the body.
3) Name the listserv something presumptive and possibly slightly offensive to some of people you decided to include as members.
4) Sit back and watch the fun as neophyte users reply, again and again, all day long, saying things like "sign me up for the list!" or "I think we should name it something else" or "great idea!" filling up the boxes of untold strangers with a deluge of unwanted email.
This just happened to me, when the forward-looking Maine Bar Association decided to create a Young Lawyers listserv. Although they named it "Young Lawyers," I think they meant "lawyers recently admitted to the Maine Bar." They didn't actually tell us what the criteria for inclusion was. They didn't tell us much. (What they did tell us, a huge bunch of people didn't read.) They did tell us that this effort would "improve communications." I eagerly await the promised improvement.