How do I get a mount?

[SugarPeanut]

Yea lvl 20 is apparently just one requirement. Follow the story line to the parts about the Grand Company stuff and youll see ^_^
I had the same thought when I first dinged 20 like - OI ! whar's mah choco !

[Arriverderci]

Unicorn is ugly lol.
At 30, you can do a quest for a Battle Chocobo too.

[NeoZehel]

When people say lvl 20 they mean the lvl 20 side quest "My Little Chocobo" AFTER the lvl 20 story quest "The Company You Keep". In order to recieve the chocobo you need to obtain 2000 seals which can be obtained only after you choose a grand company.

[Conradus]

I thought Iwas supposed to get one at lvl 20?

You'll need to do the storyline quests; when you get into a Grand Company you will then have the opportunity to buy a chocobo for GC seals (2000, I believe). That'll happen at the level 20 quests in the storyline.