Leroy Jethro Gibbs tiene reglas para su trabajo que va dando con cuentagotas a los miembros de su equipo. Las reglas vienen de su primera esposa, Shannon, como se ve al final del episodio «Heartland» 6×04. En 3×05 «Switch»  Gibbs  le dijo a Ziva que había una 50 reglas, pero por ahora no se han hecho públicas todas. Aquí hay una lista de las citadas hasta ahora:

• Rule #1: Never let suspects stay together. (Franks) 1×01 ‘Yankee White’
• Rule #1: Never screw up (over) your partner. 4×14 ‘Blowback’
• Rule #2: Always wear gloves at a crime scene. (Franks) 1×01 ‘Yankee White’
• Rule #3: Don’t believe what you’re told. Double check. (Franks) 1×01 ‘Yankee White’
• Rule #3: Never be unreachable. 3×13 ‘Deception’
• 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. 4×11 ‘Blowback’
• Rule #5: You don’t waste good. (…»You’re Good» Gibbs says to DiNozzo) 8×22 ‘Baltimore’
• Rule #6: Never apologize — Its a sign of weakness. A rule used more often than the others, but finally given a number in 7×12 ‘Flesh and Blood’ during a great Gibbs/DiNozzo moment. The first person to use that phrase was John Wayne in, «She Wore a Yellow Ribbon.» «Never apologize, mister, it. It’s a sign of weakness.» — In the episode 3×23 ‘Hiatus Part-1’ DiNozzo explains to NCIS Director, Jenny Shepard, that Gibbs took this one from «The Duke himself.»
• Rule #7: Always be specific when you lie. 1×23 ‘Reveille’
• Rule #8: Never take anything for granted. 3×10 ‘Probie’
• Rule #9: Never go anywhere without a knife. 1×13 ‘One Shot, One Kill’ & 1×20 ‘Missing’
• Rule #10: Never get personally involved on a case. (Said by Tony, agreed on by Gibbs) 7×21 ‘Obsession’
• Rule #11: When the job is done, walk away. 6×24 ‘Semper Fidelis’
• Rule #12: Never date a coworker. 1×15 ‘Enigma’
• Rule #13: Never, ever involve a lawyer. 6×07 ‘Collateral Damage’ & 7×24 ‘Rule Fifty-One’
• Rule #15: Always work as a team. 5×05 ‘Leap of Faith’
• Rule #16: If someone thinks they have the upper-hand, 
  …break it! (DiNozzo) 8×24 ‘Pyramid’
• Rule #18: It’s better to seek forgiveness than ask permission.3×04 ‘Silver War’
• Rule #22: Never, ever bother Gibbs in interrogation. 4×10 ‘Smoked’
• Rule #23: Never mess with a Marine’s coffee if you want to live. 2×09 ‘Forced Entry’
• Rule #27: Two ways to follow: — First way they never notice you, — second way they only notice you. 7×15 ‘Jack Knife’ & 7×24 ‘Rule Fifty-One’
• Rule #28: Never run with sharp objects?
• Rule #29: Never fall asleep at your desk while writing a report?
• Rule #35: Always watch the watchers. 8×22 ‘Baltimore’
• Rule #36: If you feel like you are being played, you probably are 9×01 ‘Nature of the Beast’
• Rule #38: Your case, your lead. 6×16 ‘Bounce’
• Rule #39: There is no such thing as coincidence. 7×21 ‘Obsession’

«The 40’s are for Emergency Use Only!» 7×24 ‘Rule Fifty-One’ (Mentioned by Abby)

• Rule #40: If it seems someone is out to get you, they are. (Said by Abby, agreed on by Gibbs) 7×22 ‘Borderland’ & 7×24 ‘Rule Fifty-One’
• Rule #42: Never accept an apology from someone who just sucker punched you. 9×16 ‘Psych Out’
• Rule #44: First things first. Hide the women and children. 7×23 ‘Patriot Down’
• Rule #45: Clean up your mess. Gibbs said:»Left a mess I’ve got to clean up.» 7×24 ‘Rule Fifty-One’ (See Below)
• Rule #51: Sometimes — You’re Wrong! 7×24 ‘Rule Fifty-One’
• Rule #69: Never trust a woman who doesn’t trust her man. Season 9, Episode 7, Devil’s Triangle.

Unnumbered Rules
In my country, on my team, working my cases, my people don’t bypass the chain of command.
The «Unspoken Rule» (Franks): You do what you have to do for family. (Season 8 Episode 1)
Don’t work the system when you can work the people.
Don’t stop checking and rechecking evidence until you are satisfied.
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.»
Abigail Borin, Gibbs’ also has a set of rules. The only one currently known is her Rule #1: Never Make Excuses (Ships in the Night).
Never second guess yourself in a relationship and life.

Y recuerda. . .

«Una bofetada es una ofensa, una colleja es un toque de atención (2×06, Depósito de huesos).»