I pronounce them as..

Squall- Skwall
Quistis- Kis-tis
Zell- Just like it's written: Zell
Rinoa- Ri-no-a
Irvine- Ear-Vine
Selphie- Sel-phie
Seifer- Say-fer
Quezacotl- Qwah-za-coat-el
Shiva- Shee-va
Ifrit- Ee-freet
Raijin- Rye-jin
Fujin- Foo-jin
Ultimecia- Ool-ti-may-sia
Xu- Zoo