I'll start...

1. Just because something looks *pretty close* on the map doesn't mean that it is. Get a horse.

It's been a while, MB! 100 here we come. 
 
2. Clouds. A lot of clouds. Like, clouds everywhere.

3) if you steal cabbages from an old woman, she will send bounty hunters after you....even from the grave

4) If you steal an item and then drop said item, people will happily return their own items to you.

5) Being Dragonborn is a big deal.

6) Dragons have a need for gold coins.

7) Horses REALLY want to be the heroes.

8) Giants know how to fuck shit up.

9) I've learned that it sucks when you're level 8, you kill a dragon while having very few potions and out of nowhere a forest troll appears and kills you.

10) Fuck trolls, especially ice trolls. (not that kind of fuck)

11) Watch your fire. When you spray your flame spell all over a room trying to hit your target your allies don't appreciate being set on fire. They will return the favor.

12) If a giant hits you on a downward swing, you fly hundreds of feet into the air (physics)

13 (I think?) ) Frost Trolls know how to fuck you up. 

14) Werewolves can't sleep well at night without their teddy bears.

15) If you see a stray chicken in a village, let it be. Making it your lunch will result the entire town wanting your head.

16) Cats can be bats, can be rats, can be hats, can be gnats, can be thats can be thises.

17) People let you put buckets on their head so you can steal from them.

18) In Nordic Times, giants lived three feet from one another.

19) Horses don't obey the laws of physics.

20) Horses are braver than I.

21. Sometimes guards on horses fly through the air erratically at 100 mph.

22. Even though they warn you for the traps the same npc will walk into them afterwards.

23. People tend to make really bad decisions, document them in journals or in a note, and keep that note on them until they die.

@Morien said:

16) Cats can be bats, can be rats, can be hats, can be gnats, can be thats can be thises.

Wabbajack.

24. If you think you're safe from dragons, you're not safe from dragons.

25. Shouting Fus Ro Dah at a bandit at the top of a mountain is fun. See how far one of them flies to their doom. It's also a great way to quickly dispose of Frost Trolls.

26. You grow into a class of your own design, without a need to conform to one.

27. Don't fuck with giants.

28. If a kid witnesses a murder they usually are to scared to tell anyone

29. I'd be a lot warmer and a lot happier if my belly was full of mead right now.

30. Never trust statues.

31. If you kill all of the people that saw you commit a crime, you didn't commit a crime.

32. Magelights can stick to living things...which is awesome.

33. Copping a feel on the temple statues is generally frowned upon.

34. Nords will verbally insult your race, then turn to you for help.

35. When faced with a difficult opponent out in the world, take it back to the nearest encampment you can. Not only do you get help in beating a powerful foe, but more bodies to loot with no (major) drawbacks!

36. You can set bear traps in caverns. Shoot an arrow next to it - hide - bandit comes running to sound - steps on bear trap - winning

37. Mages were throwing hadouken before it was mainstream.

38) You might be the worlds most amazing hero, the slayer of dragons, but you'll still die to a guy in fur armor and a dagger, or a bear.

39. Dark Elves look like Klingons with pointy ears, in other words, super badass.

40. Even in death dragons can still slide along the terrain

41. Lydia is sworn to carry your burden and sounds so pleased when she says it too.

42. Chickens can be witnesses to your crimes

43. Mammoths are scarier then dragons.

44. Mammoths can float 80 feet in the air but cannot survive falls from such heights.

45. Giants' clubs can and will float into the air after their master dies, presumably to return to Sovngarde.

46. Rasism is not a good thing, unless its against elves, then its just fine.

47. Dogs can talk.

48. You can become a Vampire without any knowledge of getting bit.

49. Sometimes if you kill your friends, they'll leave you an inheritance.

50. A horse will always want to fight a dragon, but a horse will never win against a dragon.