We have a sticker bandit in our house. You may have one, too. Ours is a small child (3 years old, to be exact) who randomly puts stickers in various spots in the house. If I don't take care of the stickers right away, they can be really hard to remove. Sometimes, I immediately try to rip them off the surface and they're still really hard to remove!
The Quick Tip
Saturate the sticker with vinegar and let sit for 10 minutes. Then, scrap the sticker off! I found this tip at The New Homemaker in a fantastic article about the many uses of vinegar.
I tested it out on this: