Dragon Ball Z: Shin Budokai

When selecting a transformed character hold the "R" button. You will start in the transformed state and not have to power up and transform during the game.

Defeat Teen Gohan in Chapter 3 - 9 to unlock SS2 Teen Gohan.

Defeat Cell in Chapter 3 - 8 to unlock SS Teen Gohan.

Simply beat the last chapter to unlock either character. Take the top path to unlock Vegeto and the bottom path to unlock Gogeta.

Defeat Vegeta in Chapter 4 - 7 to unlock Majin Vegeta.

Defeat Janemba in Chapter 2 - 7 to unlock SS2 Vegeta.

Defeat #18 in Chapter 2 - 3 to unlock SS Vegeta.

Defeat Kid Buu in Chapter 5 - B-9 to unlock SS Vegetto.

On the Main Menu simply press L Button and on the Dragon Radar the words "Dragon Click" will come out. Next, press the R Button to begin the mini game. The object of the game is press the R button as many times as you can before time runs out.