Before the start of the stage, use the service area to repair any damage to your car. If the car is too badly damaged it's probably time to restart, otherwise swap your dry gravel tyres for wet gravel ones. Although the Myherin stage is completely dry gravel, changing the tyres makes good preparation for the fourth stage.
The stage itself is quite an easy one to drive so avoid any silly mistakes that will leave your car in the ditch. Although the stage is misty the lights can be left off for this one as the view isn't greatly impaired. The gravel road rolls between wide open grassy areas where the car can run off the road safely and narrow tracks lined by rocky banks leading up to dense forest. Add to this a smattering of narrow gates (only one will really catch you out though) and you have Myherin.