Start as a local "maker/hacker" user group, set up a mailing list, see if any of the local Universities more techy departments will let you mass mail their students an invite to the user group once (or maybe once a year if it gets going). Start meetups with people on the mailing list, when there's enough people get the "back room" of a pub/bar booked for monthly meetings.
Don't over emphasise 1 skill set, you want software guys as much as hardware guys, you want people who can do woodwork as much as a good fabricator/welder.
Don't go in there saying "We're going to set up a Hackspace," at most "We hope we can one day do this in our own place one day."
Don't go full in when you think you have enough members to just manage it, wait until you have more than enough.