The first thing to do is try to ensure that your dog is clean and groomed before taking them on a ride.
This is by no means easy to do, especially if you have been a long and potentially muddy walk with you four-legged pal, but is nonetheless the logical first step.
The next best thing to do is to use materials that are easy to clean and wipable.
On the floor, we would recommend using plastic or rubber-based floor mats or plastic lining.
Try using seat covers - there are loads of options on the market that are specially designed for dogs. Alternatively, you can use a plastic cover for your seats, which may not look as good as purpose made seat covers, but will certainly do the job.
Covering your car seats is especially effective if your original seat covers are upholstered.
Also, consider keeping a supply of cloths, lint rollers, air fresheners in your trunk, just in case.
If possible try to clean your car after your dog has been inside it. The initial effort will be rewarded as you will have less dog hair and smells to content moving forward.