Not tips for a "democracy" but a "good, tolerant community":
- Use a boilerplate rules list like "no spam, no personal attacks, no hate speech, don't be obnoxious, etc." (but more specific, e.g https://www.statsoc.org.au/Forum-rules or https://macrumors.zendesk.com/hc/en-us/articles/201265337-Fo...). Have a "no politics" rule unless you want culture warring on your platform for whatever reason.
- Then you enforce the rules as you see fit. The final rule should be "moderators have discretion" and if someone is pushing against the rules and/or irritating others, ban them. At the same time, be lenient and give second and third chances at least for non-blatant offenses; escalate, first with a warning, then with a temp ban, then a longer temp ban, etc. It's a careful balance, but if done correctly, your form will be both tolerant and not dominated by assholes.
- To prevent spam and banned users opening new accounts, either: make the form invite-only (where users can invite others) and screen applicants; charge a small fee for signing up; require flexible proof of identity (e.g. one of: phone #, Google account, GitHub account, Facebook account, etc.); require new user posts to be approved by moderators before they show up; or something else. This will make it significantly harder for your userbase to grow, and many people will refuse to sign up, but it will be hard and some people won't sign up anyways.
- If your forum grows enough, you can recruit moderators. You need enough people and activity to select moderators who you trust, because every time you override their moderation or kick them beyond "very rarely", you look worse (more incompetent, power-tripping, incoherent) and the overall community "vibes" become slightly more toxic.