Rule #1: Never let suspects stay together.
Rule #1: Never screw over your partner.
Rule #2: Always wear gloves at a crime scene.
Rule #3: Don't believe what you're told. Double check.
Rule #3: Never be unreachable.
Rule #4: The best way to keep a secret? Keep it to yourself. Second best? Tell one other person - if you must. There is no third best.
Rule #7: Always be specific when you lie.
Rule #8: Never take anything for granted.
Rule #9: Never go anywhere without a knife.
Rule #12: Never date a coworker.
Rule #15: Always work as a team.
Rule #18: It's better to seek forgiveness than ask permission.
Rule #22: Never, ever bother Gibbs in interrogation.
Rule #23: Never mess with a Marine's coffee if you want to live.