Fusion/Character Unlock Hints:
Must be done in Dragon mode. To get all techniques you need 10000 kills and complete the ship.
Dabura - Get over 100 Kili
Gotenks (Fusion) - Get to the Hyper Bolic Time Chamber in Dragon Mode
Kid Buu - Get over 5000 Kili
Majin Buu - Get over 1000 Kili
Majin Vegeta - Beat Majin Vegeta before Buu's egg hatches
Super Buu - Get over 2000 Kili
Vegetto (Fusion) - In the city when Supreme Kai tells you about the Potara earrings, go to him to get them. When Vegeta comes, give him the other earring.
Character Unlock Hints:
Must be done in Dragon mode
Android 16 - Beat Android 16 with Goku
Android 17 - Beat Android 17 with Piccolo
Android 18 - Beat Android 18 with Krillen
Android 20 - Beat Android 20 with Goku
Cell - Beat Cell with Goku
Frieza - Beat Frieza with Goku
Future Trunks - Beat Vegeta on Namek with Kid Trunks
Ginyu - Beat Ginyu on Namek with Vegeta
Gokule - Get Goku and Hercule's breakthrough
Hercule - Beat Fat Buu with Saiyaman
Kabitoshin (Potara) - Collect 7 Dragonballs and wish for the capsule from the Dragon
Nappa - Beat Nappa with Vegeta (first unlock Vegeta and then start Dragon mode again)
Raditz - Beat Raditz with Goku
Recoome - Beat Recoome with Goku
Saiyaman - Beat Cell with Adult Gohan only
Supreme Kai - Beat Supreme Kai with Goku
Teen Gohan - Beat Cell for the last time on Supreme Kai's planet with Adult Gohan
Tiensha - Get Tien and Yamcha's breakthroughs
Vegeta - Beat Vegeta with Goku on Namek.
Vegetto (Potara with Vegeta) - Collect seven dragonballs and wish for the capsule from the Dragon.
Videl - Beat Super Buu (with Gohan absorbed) with Hercule.
Yamcha - Beat Nappa with Tien
Unlock Hints:
Adept World Tournament - Unlock 16 Characters, then buy it from Bulma
Advanced World Tournament - Unlock all 29 Characters, then buy it from Bulma
Babidi's Ship - Collect all 7 Dragon Balls and then wish for it from Shenron.