Use your co-driver's gear recommendations to know when you can speed up and slow down. If he warns you about an upcoming corner that should be taken in second gear, slam on the brakes.
Try and repair your vehicle evenly, but put the most time into transmission, tyres, and suspension.
The button in the top-right corner will immediately bounce you back onto the track. Use it if you've really gone off the road and it would take too long to get back on course.