Steering Wheel Mounts: A steering wheel mount usually snaps on the steering wheel of a car without too much assembly. A good feature is to be able to easily remove the mount and tuck it under the car seat while the laptop mount is not being used. A steering wheel mount will require that you don’t have the laptop mounted while driving the car.
No frill laptop mounts: These use existing infrastructure in the car. Example: they use existing seat bolts. Many of these will allow the laptop to stay mounted in a moving car. Ability to mount a laptop 
in a car without drilling is key if you have multiple cars. Good quality auto laptop mounts will come with ability to absorb vibrations. While choosing a car laptop mount make sure the mounting mechanism is specific to your model.
Car desks: These provide work surfaces to put laptop and accessories. Some of them have efficient slide-out design to save space and yet be useful when you need to spread out the work. Using a laptop on a rear seat tray is straightforward. A back-seat based desk simply attaches to the back of the front seat. Be careful before using a general purpose back-seat tray – it may not be strong enough to hold the weight of your laptop.