With an axe

No seriously I cut them with a saw the reason I like to do it is at, a pro shop or mail order place they usually only cut the arrow from one end where I like to take an 1" off the nock end then cut to lenght.

Also if you have your own jig then as Ewolf said you can repair one vane/feather.
Over time you can save a lot of money by making and repairing your own arrows.

If you are just starting out then get the Arizona Easy Fletcher it does all 3 at the one time and is simple and easy to use.

Check out ebay for the arrow saw you can pic up some bargains there.