Just pull it up if it's small enough. You may have to follow underground stems back. Where it's got really established - say growing up a tree - you may have to settle for cutting a chunk out of the main trunk and waiting for the top growth to die, which can take some time if it's a variety with aerial roots and you're in a rainy climate. Take a lump about an inch wide out of main stems so they can't rejoin and continue growing.

Ivy's one of those plants you have to keep on at in my experience.