Successfully complete one of the following tasks to get a trophy:

A Real Go Getter!: Win every Transporter event. 
Autovia Avenger! (Gold): Beat El Machismo. 
Big City! (Gold): Beat Stinger. 
Big Ham! (Silver): Complete every Photo Op. 
Crowned Karter! (Silver): Win every Guido Kart event. 
Daring Devil! (Gold): Score 5500 points in the Mater the Greater event. 
Drift Master! (Silver): Score 4500 points with a single drift. 
Luigi's BFF! (Silver): Win every Tire Find event. 
Mack Track Medalist! (Silver): Score 4000 points in the Mack Track Challenge 
event. 
Mini Master! (Silver): Win every Mini Game event. 
Mooo-ving Along! (Silver): Win every Tractor Stampede event. 
Ole'! (Gold): Score 25000 points in the Materdor event. 
Perfectionist! (Silver): Win every Autocross event. 
Pluggin' Away! (Silver): All Sparkplugs collected from all races. 
Podium Perfection! (Silver): Win every circuit race event. 
Santa Carburera Champ! (Gold): Beat Candice. 
Sprinter! (Silver): Win every Point to Point Race event. 
Team Player! (Silver): Win every Academy Challenge. 
The Champ! (Gold): Beat Chick Hicks for the Title. 
The Law! (Silver): Win every Sheriff's Pursuit event. 
Tokyo Triumph! (Gold): Score 25000 points in the Tokyo Mater event. 
Trophy Collector! (Platinum): Earn every trophy.