A new addition to the Final Fantasy series is introduced in FFX2 with the possibility of receiving one of multiple endings. In all, there are six. This guide has minimal spoilers (reveals boss name and locations), and is really just explaining how to get the different ones.

Bad Ending:
To get the bad ending, you simply need to lose the fight against Vegnagun. If you draw the fight out so it takes too long, you will also lose and get this ending.

Normal Ending:
This is the default ending. Depending on what extra stuff you did it will be modified or have scenes added to it. Just win the game and there you go.

Normal Ending 2:
This is the same as the previous ending, except you see a short extra scene. To get the ending, tap X continuously in the field of flowers after the Chapter 5 Complete message appears (Farplane Abyss). You may not get this ending if you get the Good ones listed below.

Good Ending:
There are two things you must do to get this ending. First, you must talk to Maechen in Guadosalem in Chapter 3, and, again in Chapter 3, when Yuna is in the Farplane, tap X until you hear whistling 4 times. Then, at the end of the game in the Farplane Abyss, when you hit X, a fayth will appear. Answer "Yes!"

Good Ending 2:
Do everything above except when you see the fayth, select "It's better this way" instead of the first option. The first option is, in general, considered better.

Perfect Ending:
Do everything as needed for the first good ending except you must have 100% completion (or more. 103% is possible). This will give you the normal ending, the good, and an extra clip at the end of all that.