Right after leaving Lindblum
Quina is a fictional character, which is optional to choose. Quina can be recruited right after leaving Lindblum.
Go north from Lindblum
Follow the northeast direction right after you leaveLindblum until you can find a dense circular forest. It would help if you headed into the woods, as this is the place where Quina can be recruited.
Reach the swamp
You will see Qiuna trying to catch the frogs while running and reaching through the tall grass up to the swamp.
Grab the frog on the ground
It would be best if you grabbed the frog, roaming on the earth, once you start heading to the right.
Talk to Quina again
You are enabled to talk to Quina now. (See Why many people like Final Fantasy 9?)
You will be asked if you want Quina to join
You will be provided with an option of whether you would like Quina to join the party? And you need to select ‘Yes.’
In case you missed Quina
In case you selected that you do not want Quina to join the party, you will still be forced to get her later in this game. However, if you will select her in the first go, it will make the troublesome area of the game smooth and effortless. (See How To Win Final Fantasy 9 Card Game)