First, make sure that your pet has proper identification on him or her at all times. This can be something as simple as an ID tag on his collar, but a more permanent solution would be the use of an implantable microchip.
Next, make sure you have copies of vaccination records and needed medications easily accessible during the trip. You can go to healthypet.com to locate AAHA veterinarians along the way or at your destination.
And finally, do your homework. Some airlines and travel sites may require a health certificate for your pet. This document must be dated within 10 days of the start of your travels.