Newbie Top Tips

Don't spend money unless you have to.
(We know buying a complete level 2 car before race 1 is tempting - but it really isn't a good idea).
ONCE AGAIN - DON'T SPEND MONEY!
Don't use any race risks, as these will destroy your car (Overtaking / Defensive / Clear Track / Malfunctioning). If you do choose to run with risks, remember that 40 is considered ridiculously high for Rookies - therefore don't blame the game if you fail to finish, or need to replace all your parts after just one race.
Save, save, save all data. Save everything.
This information will help you form better race strategies amongst other benefits.
Look at the weather - and triple check you are using the correct tyres (Wet tyres when it's raining!)
Your driver is the most important factor. Get a good driver with the correct attributes and you will challenge for wins even with a poor car.
Don't offer your driver a ridiculous salary. The figure you are offering is per race, therefore anything over $3mil is going to make things difficult (although not impossible if you can handle your finances sensibly).
Plan ahead. Sometimes it's better to accept you won't finish the next race, and choose to smoke rather than get into financial difficulty.
Loads of tips in the forums so learn how to search!
Get supporter status. Not only does it help the game it also saves a lot of data for you.