[From gibbsrules.com and wikipedia]
2. Always wear gloves at a crime scene.
3. Don't believe what you're told. Double check.
3. Never be unreachable.
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.
6. Never apologize. It's a sign of weakness.
11. When the job is done, walk away.
12. Never date a co-worker.
13. Never ever involve a lawyer.
15. Always work as a team.
16. If someone thinks they have the upper hand, break it.
18. It's better to seek forgiveness than ask permission.
22. Never ever bother Gibbs in interrogation.
23. Never mess with a Marine's coffee, if you want to live.
38. Your case, your lead.
39. There is no such thing as coincidence.
42. Never accept an apology from someone who just sucker-punched you.
44. First things first -- hide the women and children.
45. Clean up your own mess.
51. Sometimes you're wrong.
69. Never trust a woman who doesn't trust her man.