All characters and courses
Remove all memory cards from the PlayStation. Then on controller two, when the screen flashes just before the Hot Shots logo appears during the opening sequence, hold L1 + L2 + R1 + R2. Keep those buttons held, and press Up(2), Down, Up, Left, Right(2), Left, Up(2), Down, Up, Left, Right(2), Left on controller two while the Hot Shots logo is in motion. If you entered the code correctly, you will hear the sound of a wood driver.
Left or right-handed golfer
At the character selection screen, highlight a golfer, then hold L1 and press X.
At the course selection screen, highlight a course, then hold L1 + L2 and press X.
While playing a game, press L1 + L2 + R1 + R2 + Select + Start.