do you mean taken off ?,thats how i read it .if so it should peel off ,you may have to lift it first with a sharp blade but after that depending on whats been used it should come of easily
Agree with Ste, do not use a blade, you'll chip the paint.
Heat gun, or hair dryer, lifts them quite well,, although you will find it much easier in a warm garage or on a hot day (warms the metal on the car).
When you've taken them off it will likely leave a gluey residue, and the paint under the vinyl will be much brighter than the exposed paintwork. You can clear this up with a lot of elbow grease, or, what I did with one of mine after taking the vinyl off, was to drive it down to the American Car Wash and after two days and eighty notes it looked fantastic.
If it's the plastic/metal words then a heatgun to melt the glue is the way to go. If it's a sticker, the same applies.
If, when you remove the wording, there is still adhesive residue left, simply spray a little WD40 onto it and rub it with a microfibre cloth. Removes glue like a treat.