Once you have the puppy or dog over the initial vomiting phase on short trips (the advice given by K9 Trainer is SoCal is right on the money) be sure to visit fun places, not just the groomer, vet, or boarding kennel. Frequent trips to play at the park, visit relatives, etc, will give the dog happy experiences, which he will relate to the car trip, which will make him more comfortable.
Some dogs do better in the front seat. Some do better in the back seat. Experiment.
Good Luck!
Lucy Gerold
North Country Kennels
http://www.mixedbreedpups.com