Time for some NCIS - Night interwebz... - The Rules of Gibbs
Rule 1: "Never let suspects stay together." - revealed in the Season 1 premiere episode, Yankee White (episode).
Rule 1: "Never screw over your partner." - revealed in the Season 4 episode, Blowback (episode). McGee also stated this rule to Ned Dorneget in Need to Know (episode). McGee also mentioned to Abigail Borin in Ships in the Night (episode) that rule number one has been taken twice, showing that he knows that there are two number one rules.
Rule 2: "Always wear gloves at a crime scene." - revealed in "Yankee White".
Rule 3: "Don't believe what you're told. Double check."- again revealed in "Yankee White".
Rule 3: "Never be unreachable" - revealed in the Season 3 episode, Deception (episode) although Gibbs has been known to be intentionally unreachable. The rule was shown in Rule Fifty-One (episode) in the background when Gibbs opens the box.
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." - revealed in the Season 4 episode, Blowback (episode)
Rule 5: "You don't waste good." - revealed in the Season 8 episode, Baltimore (episode).
Rule 6: "Never say you're sorry. It's a sign of weakness." - This rule has been mentioned throughout the series, but it given a specific number until Flesh and Blood (episode). The rule is also a direct reference to John Wayne's catch phrase in She Wore A Yellow Ribbon (John Ford, Director). Wayne said: "Never apologize, mister, it's a sign of weakness." to subordinates in a military situation. DiNozzo notes the connection in Hiatus Part 1 (episode). Mark Harmon's career has paralleled John Wayne's. They both were quarterback of their southern California college football team, both went into acting. (Harmon's father, Tom Harmon, was a Heisman Trophy winner and actor & announcer as well.) Note: This is continuously told to Tony, Ziva and Tim through a smack to the back of their heads.
Rule 7: "Always be specific when you lie." - revealed in the Season 1 finale episode, Reveille (episode).
Rule 8: "Never take anything for granted." - revealed in the Season 3 episode, Probie (episode) although Gibbs also quotes it as being "Never assume" during the Season 9 episode, Rekindled (episode).
Rule 9: "Never go anywhere without a knife." - revealed in the Season 1 episode, One Shot, One Kill (episode) although it's sometimes quoted as "Never leave home without a knife" or "Always carry a knife."
Rule 10: "Never get personally involved in a case." - revealed in the Season 7 episode, Obsession (episode) and again referenced by the new SECNAV Clayton Jarvis in the Season 9 premiere episode, Nature of the Beast (episode) as the number one rule in Washington politics.
Rule 11: "When the job is done, walk away." - revealed in the Season 6 episode, Semper Fidelis (episode).
Rule 12: "Never date a co-worker." - revealed in the Season 1 episode, Enigma (episode).
Rule 13: "Never, ever involve lawyers." - revealed in "Collateral Damage". Rule 51 is written on the back of the card containing Rule 13 in "Rule Fifty-One".
Rule 14: "Bend the line, don't break it." - revealed in Anonymous was a Woman (episode).
Rule 15: "Always work as a team." - revealed in Leap of Faith (episode).
Rule 16: "If someone thinks they have the upper hand, break it." - revealed in the Season 8 finale episode, Pyramid (episode).
Rule 18: "It's better to seek forgiveness than ask permission." - revealed in Silver War (episode).
Rule 22: "Never ever bother Gibbs in interrogation." - revealed in Smoked (episode).
Rule 23: "Never mess with a Marine's coffee... if you want to live."- revealed during "Forced Entry".
Rule 27: "There are two ways to follow someone. First way, they never notice you. Second way, they only notice you." - Jack Knife (episode) and "Rule Fifty-One".
Rule 35: "Always watch the watchers." - revealed in "Baltimore".
Rule 36: "If you feel like you are being played, you probably are" - revealed in Nature of the Beast (episode).
Rule 38: "Your case, your lead." - revealed in Bounce (episode) placing Tony as temporarily in charge of the team, and also in Phoenix (episode) with Ducky as leader.
Rule 39: "There is no such thing as coincidence." - revealed in Obsession (episode) although DiNozzo states that Rule 39A is "There is no such thing as a small world" during Canary (episode).
Rule 40: "If it seems like someone is out to get you, they are." - revealed in Borderland (episode).
Rule 42: "Never accept an apology from someone who just sucker punched you." - revealed in Psych Out (episode).
Rule 44: "First things first, hide the women and children." - This rule number was mentioned in "Patriot Down," but was not stated until "Rule Fifty-One."
Rule 45: "Clean up the mess that you make." - revealed in "Rule Fifty-One" although it's also stated as "Never leave behind loose ends" in Hiatus Part 2 (episode).
Rule 51: "Sometimes you're wrong." - Created by Gibbs in Rule Fifty-One" by writing it on the back of the card containing Rule 13. It is unknown if his coworkers are aware of this rule.
Rule 69: "Never trust a woman who doesn't trust her man." - revealed in Devil's Triangle (episode).
"Never date a woman that eats more than you do." - as said by Tony in Singled Out (episode).
In my country, on my team, working my cases, my people don't bypass the chain of command"- revealed by Gibbs during a talk with Ziva in Switch (episode).
The Unspoken Rule- as revealed by Franks- You do what you have to do for family- revealed in Spider and the Fly (episode).
Don't work the system when you can work the people- revealed in Hung Out to Dry (episode).
Don't stop checking and rechecking evidence until you are satisfied.
If you want to find something, you follow it. (Said by Gibbs to Mike Franks in Deliverance (episode) with Gibbs adding that he learned that one from Mike).
Besides Rule 13, Gibbs has 6 other rules involving lawyers, but, according to DiNozzo, "You only need to know number 13; it's the umbrella one."
Never second guess yourself in a relationship and life.