Most people will suggest using goo-gone or some such thing, but that's if you dont really feel like keeping the sticker, which I am inmagining you do.
What you do is get a new loose razor blade, the sterotypical kind that have a rectangle shape with a hole in the middle and one long sharp edge. IF you are very careful, and hold it at just the right angle, you can slide it under the sticker and slowly work it to the other end, seperating the sticker from the thing it is stuck to.
I have done this many many times, and if it is just a sticker, especially a fresher one, like these are, it will peel off super easy. The only thing to worry about other than cutting yourself which really shouldnt be an issue, is if you dont hold the edge so it slides just so, it can catch on the sticker and cut it on one edge or another, though if you are properly slow, even this isnt a big deal because you can back up a bit, and slide under the cut before it gets to large, and the sticker will look fine when you stick it somewhere else.
Practice if you can on some stickers or some such. It's really very simple if you have the razor and the patience.