This is a community wiki article for everyone to write a list of unwritten rules in Eve Online. If you change a rule in the main part of the article, add an answer to indicate why.

1. Real Life (tm) ALWAYS comes first
2. Eve Online is a game. Enjoy it!
3. Never undock unless your medical clone can hold all your skillpoints
4. Never undock a ship that you can't afford to lose (fittings and cargo, included) this goes for the stuff in your skull as well (Implants)
5. No space is safe space. CONCORD punishes, it does not protect.
6. ALWAYS get FULL insurance on any ship you fly.
7. ALWAYS use warp-to-0km when traveling in Hi-sec/Low-sec.
8. NEVER warp to 0km on gate or station in 0.0, unless you know what is happening at the destination (or you're the only one in system)
9. If it sounds too good to be true, it probably is. Paranoia pays dividends!
10. Never haul more than 20 million worth of goods into Jita in a T1 hauler
11. Just because you CAN fly something doesn't mean you SHOULD
12. Always keep local open in low/null sec space
13. Never go AFK in a low/null sec system while undocked. It is a risk in high sec, too
14. Always check the map for activity when traveling through low/null sec
15. Never mine solo in a barge/exhumer in low/null sec
16. Always make safespots in low/null sec systems that you visit frequently
17. ALWAYS listen to your FC you are an extension of his will.
18. HAVE your session timer showing and beware of short warps.
19. NEVER Fit ECM Burst, unless you know what your doing...Then you won't fit ECM Burst

And some less serious ones

1. Smartbombs ain't that smart.
2. You are not Superman; Cruisers and tackler-frigates pilots take note.
3. Sitting in space in your pod is Nature's way of telling you to slow down.
4. If it's stupid but it works, it isn't stupid.
5. Try to look unimportant; the enemy may be low on ammo and not want to waste a bullet on you.
6. The enemy diversion you're ignoring is their main attack.
7. The enemy invariably attacks on two occasions: 1. when they're ready. 2. when you're not.
8. There is no such thing as a perfect plan.
9. The important things are always simple; the simple are always hard.
10. Teamwork is essential; it gives the enemy other people to shoot at.
11. Incoming fire has the right of way.
12. No combat ready unit has ever passed inspection - No inspection ready unit has ever passed combat.
13. If the enemy is within range, so are you.
14. Anything you do can get you killed, including nothing.
15. Make it too tough for the enemy to get in, and you won't be able to get out.
16. If you take more than your fair share of objectives, you will get more than your fair share of objectives to take.
17. When both sides are convinced they're about to lose, they're both right.
18. Professional soldiers are predictable; the world is full of dangerous amateurs.
19. Gang/Fleet experience is something you don't get until just after you need it.
20. You're only better than your enemy if you kill him first.
21. Just because you have an unbreakable shield or armour tank, doesn't mean you don't have exposed areas...
22. Give an order, then change the order, will get you disorder.
23. Never be first. Never be last. Never volunteer for anything.
24. Not even the podded have seen the end of war!
25. DO NOT pick a fight with a superior force unless you are fighting on your terms, or you like waking up as GOO in station.
26. Prepare the best you can for a fight but bare in mind no Strategy survives the first engagement with an enemy.