First, teach your puppy to enter and sit calmly while the car is stationary. Keep sessions short. Reward with quiet praise and treats.
Next step is to encourage them to get into the car with the engine running, again using treats and praise.
Once your puppy is happy and calm in the car, start with short trips with each successful trip getting progressively longer.
Ensure your puppy associates the car with pleasant things first, such as going to the park to play.
For longer trips, make regular stops. Just like us, dogs need to stretch their legs and toilet every couple of hours.
Some puppies may also feel more reassured in a travel kennel or carrier. Alternatively, use a leash or a harness to attach to the seat belt to restrain your puppy. This will prevent them from moving around in the vehicle.
Whether in a kennel or not, provide your puppy with a comfortable blanket and toys.
Some puppies can be affected by motion sickness. Try not to feed your puppy for at least 4 hours before travelling (but do not limit water).
Keep the vehicle well ventilated. Never leave your puppy unattended in the car on a warm day.