One thing I would say if you want your pup to be a good traveller is to work on making it a happy experience from the start. Many pups have never been in a car before their trip to your home (or if they have, it was a not very pleasant trip to the vet), so their first experience is anxious and stressful. Add in possible motion sickness, as in my papillon Sophy's case, the stress can be overwhelming - leading to drooling, vomitting, and general unhappiness all round! It took many hours of desensitising and counter conditioning to get Sophy able to travel without being ill, and there are still routes I avoid.
To sit with a dog on a hillside on a glorious afternoon is to be back in Eden,
where doing nothing was not boring- it was peace.
~ Milan Kundera