Make sure you take into consideration the weather you will be traveling in – both your present situation and the likely temperature of your destination. If it is likely to be very hot then you can put a frozen water bottle in the carry cage wrapped in a towel for something cool for the cat to lean up against. If it is going to be cold then make sure the carrier is in a draft-free spot in your car while still allowing good air flow. It is wise to line the carrier well with newspaper and absorbent cloth in case an accident happens, and take some spare familiar-smelling bedding if you need to replace it.
The cat may meow initially or even throughout the whole journey – speak calmly and reassuringly to it but resist letting it out of its carrier. The noise will probably drive you mad but the cat is unlikely to be suffering; just voicing its dislike of the situation! Eventually the constant motion and noise of the car will probably induce it to sleep or at least to settle down.
*This information was gathered from http://www.fabcats.org