Superfly:
Get the "Crane's Eye View" trophy. 

Custom Bee motorcycle:
Get the "World's Highest Jump" trophy. 

Custom Playa motorcycle:
Get the "Dominate 125cc Pro Race Season" trophy. 

Special Fire motorcycle:
Get the "Dominate 250cc Pro Freestyle Season" trophy. 

Special Tiger motorcycle:
Get the "Dominate 125cc Pro Freestyle Season" trophy. 

Custom Water motorcycle:
Get the "Dominate 250cc Pro Race Season" trophy. 

Cameron Steele:
Get the "World's Longest Jump" trophy. 

Extra track editor barriers:
Get the "Dramatic Entrance" trophy. 

Extra track editor movable objects:
Get the "Impossible Stoppie" trophy. 

Extra track editor ramps:
Get the "Impossible Wheelie" trophy. 

Balloon toss mini-game:
Get the "Safety First" trophy. 

Wheelball mini-game:
Get the "Mega Stunt" trophy. 

Elrod the Viking:
Go to the Rock Ridge freestyle track. Go to the left until you notice the chair lift. 
Head downhill to the lower tower. Look for the stone ramp to the right (while still 
facing downhill). Get your speed up to about 45 mph, preload, and jump to the 
tower and stop on top of it. You must now travel up to the higher tower riding on 
the cables. When you reach the other side, will get the "Lift Tower Challenge" 
trophy and unlock Elrod the Viking. 

Sal the Alien:
Go to Fox Creek, jump through the fence, across the canyon, and into the ghost 
town. Pull up next to the church and bunny hop into the graveyard (hold Clutch, 
Rev Motor, Preload suspension, hold Back, release Clutch and Preload when the 
suspension is loaded to the max). From the grave yard, jump to the lower roof 
platform covering the doorway to the first shop. Continue jumping from roof to 
roof until you get to the end. From there, jump to the back of the building's roofs 
that you were just on. The last ramp will take you up to a rock land bridge (very 
difficult to land). Jump from the land bridge down to a ledge leading to an open 
mine shaft. Follow this passage into the military base and down to Sal's spaceship. 
Finally run past the ship to a room where Sal is being held in suspended animation 
to get the "Find Out The Truth" trophy and unlock Sal the Alien as a playable rider. 

To get the secret on Fox Creek, get over the fence and follow the white barrels. 

Custom Zebra motorcycle:
Go to West Valley Freestyle in one player mode. Go down to the basement and go 
off one of the jumps. It will take you to a place on top. Follow the way then do the 
big jump at the end to complete the "Brave The Vertical Drop" challenge. 
The "Trophy awarded" message will appear and you unlock the Custom Zebra 
motorcycle. 

Extra track editor platforms and Station Z:
Get the "Cross Training" trophy. To do this easily, participate in an exhibition race 
under the hard difficulty setting. Set the laps to "3" and opponents to "0". It is best 
to use a Super Cross Track because you will need a lot of jumps. Run the race and 
do tricks until you hit 5,000 points. You will automatically get first place because 
you are the only one on the track. 

Easy height in Step Up event:
Contrary to what the CPU will do, you do not need to jump over the bar at all. You 
just need to reach its height level. To do this, rather than trying to jump over the 
bar and risk knocking it off, jump using the other two sides of the ramp and just 
air up next to it. You will know when you have reached the required height when 
you see your score appear at the top of the screen. All you have to do now is stick 
the landing. 

Easy money:
Go to any tutorial and complete it. Return to the tutorial menu and select any 
tutorial. Immediately before you begin, press Start and quit. You will get more 
money. Do this as many times as desired. 

Easy first place trophies:
Go to an exhibition race and set it to "Easy", players to "None" and laps to "One". 
Race the tracks that you need first place trophies in. This works on race trophies 
and freestyle trophies. 

Bar jump:
When doing the bar jump in career mode, let the CPU player go first. When you 
jump over the bar and land, he should also be coming to jump. Run into him and 
he will lose speed. He now cannot get over the bar.