Select the Thunder Challenge or Lightning Challenge at the game mode screen. When done so complete the various challenges to get new Thunder Plates. The Plates are awarded randomly from game to game -- winning a certain track with a particular driver will not unlock the same Plate between games.
Night tracks and alternate tracks
Race at the desired track in quick race mode under the veteran difficulty setting. You'll have to win the race to unlock a night or alternate version of it.
Easy paint schemes
To unlock your favorite driver's paint schemes easily do the following. First, set the difficulty level to veteran or legend. Then, set the race length to 3%. Turn on unlimited tires and fuel and turn off damage. Go into quick race and choose the driver whose paint scheme you want to unlock. Choose Daytona Night (Pepsi 400). Before you qualify, go into car setup and set the transmission to manual. Set the gear ratio to 5. Exit out and qualify. You will notice your car is much faster than the others. You are running it at over 9500 rpm (about 193 to 198 mph). No one will be able to catch you. The race is very quick. In less than an hour's time, you can unlock many driver paint schemes.
Make sure all races are set on ten percent race length. Drive into the grass and spin out on lap four, rather than crash. This way, your car is not damaged and you are better able to draft. It also works on lap 7 of all 26 lap races under the 10 percent setting, and on lap 12 or 13 of 39 to 40 lap races.
Daytona: Easy win
Make sure the race is set on ten percent race length. Then, cause a crash on lap four. If done correctly, there should be a caution. Go into the pits, and ignore that fact if no one else also enters. You will probably be last, but there will soon be another caution and the leaders will come in. Stay out and do not pit. After the stop, you should be in first or second place. You will run low on gas, but you will not run out. Block and you will be able to win. Also, at Daytona in career mode in the Datona 500, when you pit instead of taking four tires or right side tires, take on left side tires and enough fuel to make it to the finish. You should leave the pits in first place, providing that you came in first or near it.