Here's the most persuasive tip I know to getting a member to participate.
Persuade the member that their unique skills, experience, and expertise, can be useful to the community.
If you can convince each member of that, you will find the majority of them participate.
You can't automate this.
It goes deeper. It means having volunteers who do some research on new members, tell them what skills, experience, and expertise would be useful. Then guide the member to a place where they can put those assets to work.
On October 29th to 30th, the world's top 250 community professionals are going to SPRINT in San Francisco. Will you be one of them?