Buy a safe so you can conceal your valuables in it. You would hate for your expensive jewelry, personal family belongings, etc. to be stolen in case a burglar breaks into your home. Keep the safe hidden in a hard-to-find location like an attic or a basement closet.
Is your dog kept outside when you are away? Use him or her to help hide your spare key! Hook your key to the dog's collar in a place that is shielded from view. This is an especially good idea if your dog doesn't like strangers, and gives you easy access to get in your home.