I have found, generally very easy to peel off if done with patience and not too agressively.
That if its only been tinted recently, it has glue on the back of the tint and sticks to the window. Lots of soapy water and a blade to scrap it of to remove the glue, very occasionally it will come off with the glue if very carefull, so best to use a blade to scrap the excess glue off.