Check your tires & brakes, watch your route & fuel stops, sure as you count on having gps/cell service, you won’t. Don’t rely on the fuel gauge, use the trip meter and figure out the next fuel stop before you get to 100 miles.
Pack light, try not to bungee anymore stuff on than you have to, and what is tied on needs to be waterproof. Take rain gear, a flashlight & tools. Optional items as space allows- Tire repair kit, air pump, jump starter, fuses, electrical tape & wire, zip ties.
And..take enough money to buy fuel and food until you get home.