Major issues help unite a community. They provide a source of activity and a reason for new members to join.
Identifying, promoting and escalating these issues is part of your job.
In some industries, issues come naturally. In many, that's not the case. You can use this process.
1) Identify the relevant issues in your sector. These should be new. Use the PESTEL framework if it helps. What's new politically, economically, socially, technologically, environmentally or legally? Which will affect your members? You can take a big news story and put a topical spin on it.
2) Ask members how they feel about this issue. Use a forum post. e.g. in an expat community you might ask "I've seen the USA is trying to make it more difficult to get a visa, will this affect many of you? What are your thoughts on it?"
3) Make a news post about this. Make this a sticky thread and publish a news post/notification/e-mail/Social media update to all members of the platform. Invite all members to give their opinion.
4) Host a poll. From the opinions, identify the common themes and post them as a poll in your community. Again, invite members to participate and give their views. You may also start sub-discussions on the topic.
5) Summarize. This is important, summarize what your community has said in a news post/forum category. Tell your community what they have said. Make sure they own their own ideas in the issue.
6) Statement. Publish a statement on behalf of the community on the issue. Send it to relevant journalists, bloggers. Use data if possible (63% of members thought this would cause major restrictions on their lives). Don't neglect local and national news. This can be a good source of growth and pride on behalf of the community to be featured in any relevant media.
7) Cause. Put together a few ideas for how you would like the issue changed. It can be a political/legal change, or even a social change ("A pledge to ...."). Launch a separate page of the community to collect signatures, encourage members to contact their friends or take the pledge. Make sure this is integrated with other social media platforms.
8) Updates on progress. Keep the community and media contacts updated on the progress of your efforts. Encourage members to be more involved and do more to help your effort. Stimulate discussions on how it's going, what members can do, and sub-categories of the major issue.
9) Win / Lose. Declare victory or defeat. It doesn't altogether matter which. It's not winning or losing that matters, it's members participating in a joint activity over a shared period of time. Winning helps, but a good defeat can help members feel pride in trying (and opens the door for future efforts).
10) Update your community history. Update your community's history page about the issue. Let members make the entry if they like. Ensure all new members can see it. Perhaps give badges/unique profile customisation to members that participated.
Mumsnet have multiple issues at any single time. Yet Mumsnet is huge and there are no shortage of parenting issues. You might like to try a major issue every six - nine months.
Brands that are really sneaky might identify a product/service related issue that members might be frustrated with and begin the process there. This is especially useful if you plan to change it. It means your community will win.