Tips
Hoping to give you a bit of guidance and to save you the trouble of learning the hard way.
Scene Skipping
Though you can skip certain scenes in the game by pressing the Square button when the game is paused, doing so will cause you to lose story completion percantage. Not really worth it.
Hotspots
Unless you want to miss out on the many side quests and extras the game has to offer, avoid only visiting the labeled hotspots on your map. Try exploring the world frequently—at least one visit to each place every chapter.
Finding Rin's Travel Agency in the Thunder Plains
Rin's travel agency in the thunder plains is not clearly marked, but you will want to find this place. It is mid-way through the Thunder Plains and has a save sphere in front of the building. This comes in handy since the fiends here can be tough if you aren't leveled up enough.
* To find it when entering the plains from Guadosalam: Walk all the way to the far north of the first area map, exiting through the exit on the left hand side.
* To find it when entering the plains from Macalania Woods: Walk all the way to the far south of the area map, exiting through the exit on the left hand side.
Exiting this way from either location leads to a small area that contains the travel agency and a save sphere. If you had exited from the right hand side instead, you would have missed this area. The travel agency contains a shop that sells restorative items and a few accessories.
Be careful where you walk
In Chapter 1, when you enter the Moonflow for the first time, make sure you enter from the Celsius instead of walking in from another location. This will trigger an additional scene that you wouldn't see any other way, gaining you a bit more completion points.
Get some rest
To gain more completion points towards 100% completion, sleep in the cabin of the Celsius once per chapter. This will trigger a scene in Chapter 5 that counts towards completion. To sleep, go to the cabin and talk to Barkeep and then select rest. This also unlocks the option to have Barkeep rename your Trainer DP pets in Chapter 5.
Rare Item
The item shop in Besaid has a rare item that you can buy. If you ask the girl clerk in the shop if she has any rare items, she will give you the option of purchasing the Besaid Key for 900,000. If you don't purchase it after asking about it, the chance of her selling it to someone else goes up. This will happen each time you talk to her about rare items but don't purchase the key, so it is best to not talk to her about it until you have enough money.
Auto-Jump
When directing Yuna around cities, dungeons or even the Gullwings airship, keep the jump button pressed and you may just stumble upon unknown stortcuts and maybe the occasional hidden path or secret area. Many hidden treasures may only be obtained by jumping to a new platform, so keeping the button pressed will do half of the search for you. Your eyes, as well as luck, will do the other half. Team work!
Cheating Luck
A handy tip when using the Lady luck dressphere which will grant you good fortune when using the "Reels" abilities is, when using any of the four skills, simply pause the game. Pause still works as normal and will allow you as much time as you need when aiming for that elusive 777 jackpot. When the slots start rolling, pause and you can see what icon will be coming next. Take your time, pausing and unpausing, aligning your desired icons and win big every time!
Chapter Completion Warnings
Each chapter has certain missions, called Hotspots, which need to be completed to advance to the next chapter. After a certain point in the story, you will be taken directly to the final mission of a chapter. Sometimes this happens unexpectedly. This can be a problem if you still have side quests you need to do or areas you wanted to visit. This could also cause you to miss out on completion points.
* CHAPTER 1 - After you complete the Besaid Island and Zanarkand missions, you are flown straight to Kilika for the Chapter 1 final mission. Go visit other areas and complete side quests before you go to Zanarkand.
* CHAPTER 2 - After you obtain all three syndicate uniforms, you can get inside Leblanc's chateau. But if you have any side quests to complete, you should do so first. You won't be able to return to the Celsius once you put on the uniforms in front of Leblanc's chateau. If you get to this point and aren't ready, you'll have the option not to put on the uniforms. After you complete this mission in Guadosalam, you will be taken straight to Bevelle for the final mission of Chapter 2. Brother will fly you there with no option to go to any other locations.
