How do you rank-up your Chocobo Companion faster?

[Bouteiller]

In your character screen, there is a link to your chocobo. He/she can achieve rank 10 I think, but his level will always mirror yours. You can see how much exp they need to their next rank up on this screen. He/She takes a portion of your exp gain. Upon a rank up they get points to put into their abilities.

[Sentinel]

Ok, I hope I can get though all the misinformation here.

Your chocobo will rank up with you, regardless of what level you are. Unlike your level bar, the chocobo's xp bar is % based, which is why you cannot see exactly what the xp value the bar is. the XP gain for chocobo is calculated based on your current level compared to the level and status of the mob you just killed (weather its reg or rare etc).

What it means for you is, it does not matter if you are level 20 or level 50, the chocobo will likely gain xp at the same rate, you just worry about having him out as much as possible and kill the highest level mobs you can as fast as possible. Leavequests are a great way to rank up your chocobo.

[DSN]

As you kill enemies your chocobo gains XP, even if you are level 50 you can test this by killing a level 46+ enemy. You will see you gained XXX Experience, this is your chocobo.
On your character screen there is a little chocbo icon above your character picture, click this. This will open your chocobos character screen, here you can view current and required XP for next level.
It is slow, you are not meant to max your chocobo while leveling your first 50 class. If you are 1.0 and all 50 you need to go kill high level mobs. It has to be an enemy that WOULD give you experience points if you were eligible to gain experience points.