This sounds obvious, but it's ignored often.
Make the community about your members.
Not the brand, but the members. Communities about brands usually struggle. The concept, content, activities, and discussions aren’t interesting enough to sustain a long-term discussion.
You see this when there is a community about a brand’s products, with content about the latest product news (upcoming releases), activities asking members to vote which particular features of the product they like best, and overly-optimistic discussions about when members first used the product. This betrays a startling lack of respect for your audience.
This is often, sadly, the norm for community building rather than the exception. It’s a community in name only. It’s a marketing push for the brand trying to co-opt the concept of the community. It should be a community push co-opting the brand.
Communities about things people have a strong interest in succeed. People are rarely as interested in the brand as we think. This affects the concept, content, discussions, and activities you initiate and facilitate in your community.
Communities about brands are boring. Few brands are interesting enough to build a community around. You might be able to build a customer-service channel, but not a genuine community. You might have many customers that like you, are loyal to you, but don’t want to spend their spare time talking about you.
Conceptualize around something within the broader topic. Kotex Girlspace isn’t a community about feminine hygiene products, it’s a support community for girls when they get their periods (or just want to chat about other issues). Before you launch your community, talk to your members. Identify their biggest problems, hopes, relevancies and other interests. Build a community around that.
Make your content the local newspaper for your community. Write about what’s happening in the community. Write about interesting discussions, upcoming events, preview events, new members, and issues that affect the group. Interview members. If two members get married, write about that too. Mention your members’ milestones.
The content should be the place where people go to find what's new in the community. It helps create the narrative for the community.
Initiate activities and events
Schedule regular events and activities in your community calendar. Identify the biggest problems members have and schedule a live-discussion/expert speaker to address the issue.
Organize or facilitate offline meet-ups. Set a challenge/quiz for members and keep a regular score table. Host a week-long debate. Keep it fresh and interesting (by interesting, we mean relevant to what member’s hope to do in the future or are struggling with right now).
Facilitate and initiate member-relevant discussions
Don’t ask members how awesome your products are (this happens curiously often), ask members interesting questions about their lives. What is your biggest achievement? What do you think about an industry issue? There are no shortage of conversation starters.
Highlight the off-topic and highly-active discussions. Promote them through other channels. Encourage high levels of self-disclosure between members. Use this as social proof to promote further activity.
If you have an existing online community, the single quickest way to make it better is to make it more about the members and less about the brand (customer service channels aside). You benefit from a branded community, not branded conversations.