How do you define initial rules to avoid both over- and under-regulation?

The trap of over-regulation is creating so many rules that ordinary, good-faith participation becomes an obstacle course. The trap of under-regulation is leaving so much undefined that the community's norms drift toward the lowest common denominator. Striking the right balance at launch requires accepting that you cannot anticipate every problem and focusing instead on the small set of rules that actually shape behavior. A practical starting point is to begin with the minimum rule set that prevents the most obvious harms. Almost every community benefits from a rule requiring on-topic content, a rule prohibiting personal attacks and harassment, a rule against spam and self-promotion without participation, and a rule directing users to Reddit's sitewide content policy. These four cover the vast majority of enforcement situations in a young community and leave room for organic norms to develop before they are codified. Each rule should describe the behavior it prohibits or requires, explain the rationale in one sentence, and indicate the consequence for violation. Rules written without context are often perceived as arbitrary, and arbitrary enforcement breeds resentment. For example, "No self-promotion (Rule 4): We're here to have discussions, not to serve as a free advertising platform. Promotional links without meaningful participation in the community will be removed" is far more effective than a single line reading "No self-promotion." Resist the temptation to write rules in response to hypothetical violations. New moderators frequently draft elaborate rule sets addressing scenarios that have never occurred in their community. This wastes the goodwill of your early members, who may feel presumed guilty of offenses they would never commit. Instead, use a lightweight rule set at launch, observe the actual behavior in your community over the first few months, and add or refine rules in direct response to recurring problems you have genuinely encountered. Document the reasoning behind each new rule when you add it, so that later moderators understand the context. Rules that emerge organically from real situations are more defensible and more consistently enforced than those written speculatively.