Gibbs' Rules for NCIS Agents

Supervisory Special Agent Leroy Jethro Gibbs is Chief investigator from the NCIS television series played by Mark Harmon. These are his rules:

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: If you have a secret, the best thing is to keep it to yourself. The second-best is to 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.

Another one of Gibbs' rules which is used more often than the others, but without a number, is "Never say you're sorry, it's a sign of weakness." According to DiNozzo, another rule is "Never marry a woman who eats more than you."

There are many more as yet undisclosed.