As a noob, I had too many of these moments... So many that I can't remember all of them... But here goes the five more important ones:

1- After playing my first days (I only achieved level 7 in four days...) trying to understand the controls and the targetting of the gamepad, finally I discovered I could stop that damn annoying "auto sheathe/unsheathe weapon" every x seconds, and also destroy the damn set of targeting and make my own targetings with L1+ circle, L1 + triangle, etc....

2- After a month running to all the places with my fisher level 35, while my arcanist was only 23.... I discovered there were retainers to save my things! Instead of selling to NPCs! I discovered there were also chocobo porters, so I could use them for moving for some zones instead of ruuuuuuuuuuuuuuun....

3- Discovered the engineering and survival manual of the grand company... After already having a lot of crafting and gathering classes upgraded with sweat.

4- One day.... finally... I discovered the expert delivery... before that, my best way of obtaining seals was... Doing FATEs in Aleport....

5- It was almost two months after playing that I discovered the instances were shared with people of other servers... I remember it as if it would be yesterday, someone asked in Brayflox longstop from which server we where and I just replied: "Erhm... from Lich... Like... Everyone?"