In order to prevent your pet's hair from getting all over your car, you should brush your pet thoroughly before each car ride. This will remove any loose hairs from your animal and can help to decrease the amount of hair your pet leaves behind. Depending on your pet and the breed, you should brush their hair regularly to manage shedding. Place a blanket or towel on the seats or floor of your car. This can help to reduce the amount of hair that will get into your upholstery. It is also much easier to remove the blanket from the car to wash it once it is covered in your pet's hair. Keep your pet contained in their travel carrier while you are in the car. This is not only safe for you and your animal, but it will also help reduce the amount of pet hair in your car. Place the crate on the floor or secure it to a seat using a seatbelt so that the crate can not roll around while you are driving.

Summary:
Brush your pet before each car ride. Cover your seats with a blanket. Crate your pet in the car.