If you are a member of a group or the owner, then the first step is to have your own energy/passion for the group. Once you have that energy, working (and yes it is a bit of work) to help others feel that energy can be done.
Group membership: Consider diversity of membership. Not everyone in a community will participate, being realistic is important. In any community, participation is always low (think 10% or less), so the more members and the more diverse they are , the more participation you may get. Make sure you have regular activities , whether it's daily, weekly, bi-weekly, monthly, group members should expect some sort of activity at a predefined date/time on a regular basis.
- Consider an outreach to your group - perhaps a "newsletter" once a month....as not every member of your group is as passionate as you are nor visits the group as regularly as you do, consider ways to reach your members to alert them of information of value. If they don't want to hear what you have to share, they'll let you know and/or leave the group.
Group core team: as has been said before, don't go it alone. Consider multiple owners that share the passion and are willing to rotate engagement, outreach and adding value to the group.
- Be patient: not everyone has or will have your passion to lead or participate.