What makes a rule people follow
A rule a player understands on first reading is a rule they can follow. “No RDM” is a rule for people who already know the server; “Do not attack anybody without a roleplay reason that came out of an interaction between you” is a rule for the player who joined ten minutes ago, and they are the one breaking it.
Keep each rule to one idea, say what to do rather than only what not to do, and give an example where the line is blurry. Twenty short rules are read; four long paragraphs are scrolled past.