Start by heading southwest through the door to find a box on the floor containing Flint. Just press the X button to examine and pick it up. Take the Flint out into the main room and up through the door to the north. Go up the stairs and examine the vase holding the Withered Bouquet about halfway up. The Withered Bouquet can be used as kindling. There is also a Hi-Potion in a chest at the top of the stairs; grab it and then head back down to the fire pit in the middle of the hall. Light the fire to continue the story.
After a short time a monster will attack you and you'll be joined by Rikku, who will play an important role in the story to follow. Use her grenades to help you defeat it more quickly. If you run out of grenades just use Rikku's steal command to steal some more from the monster.
After you’re forced to work for your captors but before you leave make sure you allow Rikku to teach you how to use the Sphere Grid. Talk to Rikku one more time to get started on your next mission. The red arrow on the mini-map in the top left corner of the screen will show you which direction to swim. Swim all the way down until you reach the target of your next mission - the power station.
Once you get inside the power station move towards the front end (for the most part just follow Rikku around). When you get to the back end help Rikku start up the generator and then make your way back towards the entrance. Along the way you'll encounter the first boss, Tros.
Tros: isn’t too difficult. This boss moves around the center of the room as you fight him. The first time he moves around you'll be given two commands; choose to Stand By (recover some HP). The second time he goes around you and Rikku will be able to do the Pincer attack. You will surround him and will collectively do much more damage.
After you've defeated Tros swim over to Rikku to find a small hole in the fencing which you can use to escape. Swim through the hole and use the red arrow to guide you back up to the ship, just like before.
After a short interlude the story will continue with Tidus waking up on the beach. Swim your way over to the the Blitzball team that woke you up. Introductions will follow and Wakka will then lead you back to Besaid Village. Follow the path and swim all the way across the waterway to get to the village. Wakka is now a permanent member of the team and will remain with you throughout the whole story and he will also help make the enemy filled journey across this waterway a little less difficult.
Once you get to the village make sure to inspect and search through all of the buildings and talk to the people. After you've checked out everything head up to the temple which is located at the far north end of the village. Talk to the priest inside to continue the story and then go back out and talk to Wakka in his house. He will tell you to take a nap.
After you wake up go back to the temple. Tidus will follow Yuna into the Besaid Cloister of Trials. This is the first of six Cloister of Trials you will need to complete throughout the game. Click here for a detailed instructions on completing the Besaid Cloister of Trials.
After "rescuing" Yuna head outside and watch her summon Valefor.
At the end of the video Tidus, Wakka, Lulu and Yuna will start the journey towards the boat. You've finally got your party and the story is finally underway. Make your down the trail and up the mountain towards the beach you started at. You’ll get an introduction for each character and an explanation on how to use them effectively in battle as you go.
Continue down the path until you get to the beach. Once you arrive follow the team over to the docks and talk to all the people to receive free items; then board the boat to start the journey.
Talk to Wakka to get the story rolling again on the boat as you can’t talk to Yuna yet with that group of people surrounding her. Then go downstairs to meat O’aka XXIII. He will sell you things as a travellign salesman throughout the game. Now make your way back up to the group of people surrounding Yuna and talk to them. You’ll over hear one of them say something about Yuna’s father. Walk back over to Wakka and ask him about it. After this the people surrounding Yuna will disperse allowing you to go over and give yourself a proper introduction.
At the end of the cutscene you’ll be thrust into battle with Sin. First defeat all the bugs that come off of him and then after the explanation on how to attack from a distance switch your primary focus to attacking the fin. Lulu and Wakka are the only ones who are able to attack the fin (using ranged attacks).
The conclusion of the battle will see Sin break free abd Tidus will fall into the water. Wakka then jumps in the water to save him starting the next fight.
Sinspawn Echuilles: You must now defeat the boss Echuilles, who is a spawn of Sin. It may be a good idea to attack the smaller units surrounding the boss first. Focus on them one at a time until they're all gone; they die pretty easily. Use Wakka’s Dark Attack to keep Echuilles blind and prevent Echuilles from attacking you while you take care of the smaller units and then unleash your full strength on Echuilles.
Once you’ve defeated the Sinspawn you will get to watch a video of Sin destroying Kilika.