Make sure you have GPS in your phone as well as car. Have the offline map installed as well in case there is no cell reception during the trip. Consider a physical map as a backup plan.
Travel with your driving license, vehicle registration, insurance document, identification proof and other important papers you may be asked to furnish during the trip. Keep a copy of all documents in your phone as well.
Make your road trip delightful by selecting the best music playlist. During the long stretches of the trip, you can also put on audiobooks so that the driver has someone for company and they don't fall asleep.
Have physical money on you as well as the cards. Make sure that you have just enough that will help you get by during emergencies and for paying tolls.
Get food, a lot of it. People often get grumpy during a road trip when they are hungry. Make sure you are full and if you run out of food, take ample breaks to load up on the carbs.