If this is any one simple tactic that any community can benefits from using, it’s interviewing members.
It’s hardly a secret. Make member interviews a weekly feature.
Each week select one of your most active members and interview them for the community. Ask them who they are, what they do, how they became interest in the topic, what their best/worst memories, which other members they like best, what their thoughts are on topical issues. Make sure you get their top tips too.
Also ask them some fun off-topic stuff. Perhaps their favourite books and movies. Maybe ask them about their favourite foods or places to go on holiday.
Interviews create comparisons between members. They encourage others to participate more so they can be interviewed. Interviews also let you target more activity from specific people. You can interview people you want to participate more, or join your community.