I know alot of people have made "Rules of Minecraft" topics, so after sifting through them, I found 10 "Rules" everyone seems to agree about.

Rule 1: Never dig the block below or above you
Rule 2: When in doubt, It wants to kill you
Rule 3: Light up everything
Rule 4: Do NOT play with fire
Rule 5: Build a lighthouse so you can find your way home
Rule 6: Never trust the water level for fall survival
Rule 7: If you hear the fuse, do not look around; RUN!
Rule 8: Your greatest enemy is Murphy's Law
Rule 9: Keep everything
Rule 10: Always build your home near your spawn point