You can do these when your special meter is on full:
BS One Foot Smith: Press Up, Down, Triangle.
Samba Flip: Press Left, Right, Circle.
Sit Down Air: Press Left, Down, Circle
Complete Current Objective
First begin any goal, then pause hold L1 and enter Triangle, Right, Up, X, Right, Circle, Up, Triangle, Square, Left, Up, X. The pause menu will shake to confirm entry.
Enter one of the names listed below to create a pre-made secret skater:
#$%@!
Aaron Skillman
Adam Lippman
Andrew Skates
Andy Marchal
Angus
Atiba Jefferson
Ben Scott Pye
Big Tex
Brian Jennings
Captain Liberty
Chauwa Steel
Chris Peacock
ConMan
Danaconda
Dave Stohl
DDT
DeadEndRoad
Fakes The Clown
Fritz
Gary Jesdanun
grjost
Henry Ji
Jason Uyeda
Jim Jagger
Joe Favazza
John Rosser
Jow
Kenzo
Kevin Mulhall
Kraken
Lindsey Hayes
Lisa G Davies
Little Man
Marilena Rixfor
Mat Hoffman
Matt Mcpherson
Maya's Daddy
Meek West
Mike Day
Mike Lashever
Mike Ward
Mr. Brad
Nolan Nelson
Parking Guy
Peasus
Pete Day
Pooper
Rick Thorne
Sik
Stacey D
Stacey Ytuarte
Stealing Is Bad
Team Chicken
Ted Barber
Todd Wahoske
Top Bloke
Wardcore
Zac ZiG Drake
Unlock Everything
First you need to be playing on the first level. Press pause and hold L1. Then press up, up, up, down, down, down, square, square, triangle, circle, up, up. Then complete one goal and exit the level. Save and restart the game and you will have everything unlocked.