Perfect Manuals:
Enter keepitsteady as a cheat code. Then while playing, pause and activate the code in the options/cheats menu.

Moon Gravity:
Enter getitup as a cheat code. Then while playing, pause and activate the code in the options/cheats menu.

All FMVs:
Enter digivid as a cheat code. Then while playing, pause and activate the code in the options/cheats menu.

Hidden Skaters:
Enter the following names in Create-a-skater to unlock hidden skaters:
1337
Akira2s
Alan Flores
Alex Garcia
Andy Marchel
Bailey
Big Tex
Chauwa Steel
Chris Rausch
ChrisP
CodePirate
DDT
Daddy Mac
Dan Nelson
Dave Stohl
FROGHAM
GEIGER
GMIAB
Glycerin
Greenie
Guilt Ladle
Hammer
Henry Ji
Jason Uyeda
Jeremy Andersen
Joel Jewett
Johnny Ow
M'YAK
MARCOS XK8R
Mike Ward
NSJEFF
Noly
POOPER
Skillzombie
Stacey D
Steal2Liv
THEDOC
TOPBLOKE
TSUEnami!
The Kraken
The Swink
Todd Wahoske
Y2KJ
Yawgurt
ZiG
arrr
buffoon
crom
deadendroad
fatass
grjost
leedsleedsleeds
moreuberthaned
sik®
tao zheng
woodchuck

Easy Points:
To score big, input the perfect manual cheat then, when the goal starts (score goal's) imediatly perform a manual. While manualing use any of these moves:

Triangle + Triangle
Circle + Circle
Square + Square
Triangle + Sqaure
Square + Triangle
Triangle + Circle
Circle + Triangle
Square + Circle
Circle + Square
(supplied by: gaming-ruler)

Secret tape locations:
New Jersey: Under bridge
Manhattan: On top of electric welcome sign
Hawaii: On hotel roof
Slam city jam: Inside big T.V cube.
(supplied by: dakoto)

Drunken Man.
I call it drunken man but call it what you want it's still pretty cool. First you'll need to beat the game (doesn't matter what skill level) once you have beaten it you should get the cheats cool special and always special. Cool special make all you specials look like it did over the helicopter jump in Hawaii. Anyways go to you favorite skate park or make your own and turn those two cheats on when you do that you'll need to skate up to a rail and when your next to it pull off a Mctwist but in the middle of the Mctwist press the triangle button. If preformed correctly you should have the blurriness of the helicopter jump from then on. In order to turn it off just got to a jump (any will do and pull a special trick this will make it go away. It may take a few tries to get it right but its fun none the less. Also this may, cause you to feel dizzy after you play so be careful. And if you exit the level it will be back to normal.
(supplied by: cypher98p284)

Evil Tiki / Hawaii old school Level:
It does not matter if you beat the game or not. Just skate around Hawaii and look for the the store on the street that says Evil Tiki somewhere on the store. Then get off your board and walk up to it while pressing up on the arrow pad. In yellow letters it will say Evil Tiki. Get on your board through the tiki and you will see a levitating blue object. Ollie out of the end of the tiki tunnel and try to aim when you ollie at the levitating object. It may take you a few times to get it but dont worry, you can go in there any time you want. Once you get it it will say you unlocked the old school Tony Hawk Pro Skater 2 level.
(supplied by: Guner04)

Secret Old School Level:
This level is in New Jersey.You can find it in the goal when the Bratty kid tells you that the street is lava and you have to get some points to impress him you hace to go by the fence next to the subway building it will be on a ledge so try to grind to it and it will say you unlocked an old school level: SCHOOL II