If you must hide a spare key, try this: The key under your flower pot opens a storage shed on your neighbor's property. Among the many items inside the shed is toolbox, at the bottom of which are a dozen spare and random keys, one of which opens your home. The key under your flower pot is unlikely to be tried on the neighbor's shed. Your key is hidden among what appears to be a pile of old spare keys, which are typically deemed old keys of unknown origins. Your key, hidden in this fashion, is not likely to be linked to your house and provides an effective, albeit time-consuming, method for hiding a spare key.
source: HowStuffWorks "10 Ways to Break Into a House"
