As with just about any other query online, I strongly recommend you go to Google and search for exactly what you seek. When I go to Google and search for the game, here's what I see:

Cool, isn't it? Another way that our pals at Mountain View are making search a more useful capability. But yeah, yadda yadda, let's actually get into the cheats themselves. Do that by clicking on cheats on the top list.

There are 1.2 million matching pages on the Web, so clearly this is not only a popular game, but writing cheats is popular too. The top match is for a cheats page on the terrific site Gamespot.com:

Click through it and you'll get to the busy and confusing Gamespot site. Take a deep breath and see if you can find the cheat type categorizations:

Not bad, three cheat codes, 40 unlockables, 3 secrets, 2 glitches and 19 frequently asked questions about this popular game, Need for Speed: Most Wanted.

A smart additional strategy for this sort of cheats research is to go to the original manufacturer of the game. Most of them have a wealth of useful information to help you learn how to play better, have more useful strategies and win the game.

In this case, the game's from Electronic Arts, so its home page is on the EA site: Need for Speed: Most Wanted. Go there and dig around, lots of EA game areas have links like "Tips and Techniques" that aren't cheats, necessarily, but can help you learn how to beat the game or get better scores without resorting to cheating, which often prevents you from getting on the leaderboard...

One more: I really like 1up.com for its clean and understandable design. For example, check out their page for Need for Speed Cheats, where you'll learn:

That's just a subset of what they list, hope that's helpful. Good luck winning your next race!