Depends on how much $$ you're willing to spend and how you plan to use it.

The simplest and cheapest is the kind you put on the trailer hitch. Super easy and will do if you just drive out - ride your bike - drive back again. Not so good if you need to stop along the way to buy groceries or if you want to bring your bike on a long car holiday. They typically offer little theft protection (although you can add your own bike lock with a little ingenuity), and with most car/rack combinations you have to take off the rack to open the rear compartments. More sophisticated versions may have a lock, and may even have a hinge mechanism so you can access the rear compartment without dismantling the bike.


A good roof mount will not interfere with anything except low clearance overpasses and is easy to use. Buy one that is lockable, because some day it will be sooooooo convenient just to leave your bike on the roof.


The Thule brand is very good quality, but expensive. http://www.thulegroup.com/en/
Have a look through their catalog, you'll see the range of solutions available.