It's all dependant on how many times you flip the character square. Different numbers of flips will give you different costumes. Some characters have more than one alternate costumes. Everyones second costume takes two flips except Sonya and Tanya's which take three. Some costumes even come with different weapons!
At the player select screen highlight your player and hold START then press C-UP two or three times (depending on person) then release START and press A to start game. Your fighter should have an awesome new costume and they will take out someone else's weapon.
Below are the outfits and weapons of each character. The number before each set of clothing and weapon is how many times you will need to do the clothing code.
KAI
(1) Red Outfit w/Shoulder Strap (Ghurka Knife)
(2) Green Outfit (Ghurka Knife)
(3) Red Outfit w/Shoulder Strap (Wooden Staff)
(4) Biker Outfit (Spiked Club)
RAYDEN
(1) Blue + White Outfit (Warhammer)
(2) Red + White Outfit (Warhammer)
(3) MKII Outfit (WindBlade)
(4) Red + White Outfit (Ghurka Knife)
SHINNOK
(1) Red + Teal Outfit (Battle Staff)
(2) Black + Yellow Outfit (Battle Staff)
(3) Red + Teal Outfit (Long Sword)
(4) Black + Yellow Outfit (Boomerang)
LIU KANG
(1) Red + Black Outfit w/Tanktop (Dragon Sword)
(2) Black + Blue Outfit (Dragon Sword)
(3) Black Training Outfit (Dragon Sword)
(4) Black + Blue Outfit (Dragon Sword)
REPTILE
(1) Purple + Black Outfit (Battle Axe)
(2) Red + Black Outfit (Battle Axe)
(3) Original Lin Kuei Outfit (Black Dragon Sword)
(4) Red + Black Outfit (Spiked Club)
SCORPION
(1) Original Yellow Outfit (Long Sword)
(2) Red Outfit (Long Sword)
(3) Unmasked Grey Outfit (Mace)
(4) Red Outfit (Black Dragon Sword)
JAX
(1) Red + Black Outfit (Spiked Club)
(2) Purple + Black Outfit (Spiked Club)
(3) White Outfit w/Tanktop (Battle Staff)
(4) Purple + Black Outfit (Ghurka Knife)
REIKO
(1) Red + Black Outfit (Spiked Club)
(2) Purple + Black Outfit (Spiked Club)
(3) Red + Black Outfit (Dragon Sword)
(4) Purple + Black Outfit (Crossbow)
J. CAGE
(1) Blue + Black Outfit (Bowie Knife)
(2) Red + Black Outfit (Bowie Knife)
(3) Blue + Black Outfit (Ghurka Knife)
(4) Tuxedo Outfit (Silenced PPK Pistol)
JAREK
(1) Green + Brown Outfit (Black Dragon Sword)
(2) Dark Brown + Brown Outfit (Black Dragon Sword)
(3) Green + Brown Outfit (Warhammer)
(4) Dark Brown + Brown Outfit (Warhammer)
TANYA
(1) Yellow + Black Outfit (Boomerang)
(2) Purple + Black Outfit (Boomerang)
(3) Yellow + Black Outfit (Ice Scepter)
(4) Black Princess Outfit (Warhammer)
FUJIN
(1) Teal + Black Outfit (Crossbow)
(2) Brown + Black Outfit (Crossbow)
(3) Teal + Black Outfit (Spiked Club)
(4) Brown + Black Outfit (Battle Staff)
SUB ZERO
(1) Original Blue Outfit (Ice Scepter)
(2) Unmasked Blue Outfit (Ice Scepter)
(3) Half Frozen Blue Outfit (Battle Axe)
(4) Unmasked Blue Outfit (Dragon Sword)
QUAN CHI
(1) Blue + Black Outfit (Mace)
(2) Red + Black Outfit (Mace)
(3) Blue + Black Outfit (Bowie Knife)
(4) Red + Black Outfit (Crossbow)
SONYA
(1) Green + Black Outfit (WindBlade)
(2) Red + Black Outfit (WindBlade)
(3) Green + Black Outfit (Ghurka Knife)
(4) Purple Outfit w/o Hat (Mace)
NOOB SAIBOT
(1) Original Black Lin Kuei Outfit (Scythe)
(2) Unmasked Leather Outfit (Scythe)
(3) Original Black Lin Kuei Outfit (Scythe)
(4) Death Outfit (Scythe)
GORO
(1) Red + Black Speedos (No Weapon)
I hope this helps!
