Need for Speed: Most Wanted Tips & Tricks

You start Campaign mode only being able to achieve Heat levels 1 and 2 (City Police). By defeating certain Blacklist Rivals, you can then achieve the higher Heat levels:
Heat level 3 (State Police): Defeat the Blacklist Rival #13.
Heat level 4 (Undercover State Troopers): Defeat the Blacklist Rival #9.
Heat level 5 (Federal Authorities): Defeat the Blacklist Rival #5.
Heat level 6 (Cross' Street Racin' Unit): Defeat the Blacklist Rival #1 (final level only).
After you beat the Rockport's Most Wanted level, Heat level 5 will then consist of both the Federal Authorities and Cross' Street Racin' Unit.

When the police set up a roadblock or spike strip the easiest way to get out of it is to smash into the back of their car (The spoiler end) you will keep alot of speed and can watch the cars go flying in the air

When racing, run into lightposts, signs, benches, trees, and other objects when another racer is behind you. The things you hit might get stuck under the other car and slow it down.

If you get busted and you want to keep your money, pay the money then go back to the career menu, click on load then when you go back and play, you will have all your money back, but your heat level will go down.