Tidus - T-eye-dus (in KH I, it's pronounced Tee-dus. But in KHII, it's pronounced this way).
Seifer - SIGH-fer
Raijin - R-eye-jin
Fujin - Foo-jin
Balthier - (like in the game) Ball-theer
Tifa - Tee-fuh
Aeris/th- heiress
Lucrecia- Loo-crech-ee-uh
Rydia - Rid-ee-uh
Celes- Suh-less
Quistis- Key-stis (I've heard that this is closer to the correct pronunciation of the name than Quiss-tis, because the name is French in origin...I think).
Zidane- Zi-don