Hold the "Burnout" button and smoke the tires for a few seconds so your tires get traction right from the start. Do not hold it too long or your tires will get too slick. Use the tire temperature meter to adjust your timing.
Repairing
Each time a race is completed, you must repair your car sufficiently or it will be affected during the next race. Check your engine and tires; once they go down to 90% you must repair them back to 100%.
Upgrades
The best parts to upgrade are the adjustable suspension, transmission and computer. Gear ratios will be the simplest things to customize yourself. However adjusting the suspension and computer settings will require more skill. Some cheaper upgrades have a greater benefit than more expensive options. For example, the lightweight battery and driver diet are cheap and easy ways to improve your cars performance.