Decide or a time for your first meeting. Try to make it after work around 6 or 7. If possible Post Messages on comp.sys.newton.announce, America Online's Newton forum and Compuserve's Newton forum any User group announcements. Let NewtNews, the weekly Newton Newsletter, know you are forming an user group. Your first meetings should be informal.
Some user groups have formal Meeting and make their members pay yearly dues.
If your group doesn't have any expenses try to keep the money out of the group. Something else you might try is to go to your local Macintosh or Windows User group to recruit new members. Offer to give a Newton demonstration. Some companies will send User groups demos of software to review or for the group to raffle off. If you have a Newton programmer in your area it would be beneficial to invite them to come to Some meeting.