I would consider doing one in your local area. Depending on the size of the city, it might be a section of a larger city, or citywide if a smaller town. It will likely grow once people start hearing that you are discussing strategies to protect your rights and freedoms and have some solutions for remedy against abuse. You'd be amazed how many people have been abused by the system and feel alone with nowhere to go! Once your group starts getting some steam, then would be a good time to branch out, reach out to other groups to collaborate on project of mutual interest. With this momentum, you could then contact your local sheriff and perhaps invite him to speak to your group on a particular topic of interest. You might coordinate with the local and state coordinators of
www.nationallibertyalliance.org who are very active already working with most sheriffs in every county. Those people are also politically active and working to establish the peoples' common law grand jury in each county. You will most certainly also find other groups with similar interests so learn to research and network and you'll likely find some interesting results.
But to answer your question: How to start? I might consider a small ad in a local paper that goes something like this: "Been abused by the system? Citizens' action committee forming now. Call xxx-xxxx
You might also make up some small business cards with the same text and just hang out around the courthouse handing them out, or handing them out in the mall or anywhere. You'll be surprised how many people respond!