Watch youtube vids to try and get familiar with the circuit. I found that a better way to learn than driving it on games personally. A lot of newbies brake a lot for corners unnecessarily just as they don't know where the circuit goes. Obviously better safe than sorry but unnecessary braking in a fast section can cause issues for drivers coming up behind. Having a rough idea of where the track goes is definitely important.
Don't worry about how much power you're running. Check your brakes and suspension are good and there's no odd handling characteristics. If you're running budget pads, consider an upgrade. Don't go with budget tyres, check your pressures and check the car is in good health, no perished hoses and no leaks.
Drive within your limits, keep watching your mirror, keep to the right until you pick up speed and don't cut across to a left hand apex without being sure nothing is coming up behind you.
Oh, and enjoy!
