Successfully complete all events in World Tour mode to unlock Brett Taylor.
Successfully complete World Tour mode by finishing in first place in all events in the tenth stage to unlock alternate ATV shells for each character.
Hold any of the main controller buttons during a front or back flip to perform an alternate flip and get more points/boost.
Pause for several seconds at the start of a Freestyle race to allow the power-ups to regenerate. You can then collect all of them.