Quick start:
Hold A to accelerate during the pre-race countdown until "Set" appears. Then, tap A a few times, then hold the button again. If done correctly, you car will get a faster start when "Go" appears.

Cooler:
Win all races in challenge mode, including the drag races.

Formula 2:
Get 100,000 miles without too many fourth place finishes to unlock Formula 2. Alternately, win Exotica mode with Glide.

Glide:
Get 2,200 miles to unlock the Glide car.

Heavyliftin (forklift):
Get 5,000 miles to unlock the Heavyliftin forklift.

Lil Lightnin:
Win all the free style races.

Rail:
Win Exotica mode with Whiplash.

Rocket:
Get 100,000 miles to unlock Rocket.

Whiplash:
Win Exotica mode with Formula 2.

Cars and modes:
Win all the challenge races, complete Crusin Exotica mode twice, win all the free style races, and get 40,000 miles to unlock the Heavyliftin, Lil Lightnin, Jalopie, Bad Mobile, Hunkajunk, Skidmarks, G Ride, Cooler, Piewagon, Boxcar, Scrapin By, and Glide cars. Four more of the fastest cars that also can be unlocked Formula 2, Whiplash, Rail, and Rocket. You will also unlock Wacky and Insane modes.

Hint: Holland: Hit bikes:
When you drive around the statue, stop and look carefully to find some bikes that you can hit.

Hint: Las Vegas shortcut:
On Las Vegas, when you come to the point near the water take a right. If done correctly you should be driving on the water.