It is a good idea to flip a vehicle
to get the driver out , and then kill them.
In a warthog you can even flip a tank over by running the hog into one of the
gaps where you can see under the tank. If you do it right , the tank will flip
over, then you come around and run over the driver, or just shoot it.
Don't try this with a ghost... it doesn't work the same way. In a ghost if
you shoot the tank it will freeze up of course.
To do either , you have to get the jump on the tank or whatever you are