Indeed what 86Debris86 said, try search and you will find lots of answers, but to add to the answers;
If possible: With a 'normal' car, try race normal tyres during the rain for the whole race. I think you can go 3 laps, then you're out of gas, pit and max gas, and again race normal tyres for 3 laps, then with only 1 lap to go, do race softs and max half the gas and finish the race. Set top speed to 420 kmh! Max the car out on all installments you can buy for it.
I did this with the Veyron and won it.