I have a metal rod (I forget what sort of metal) about 4 feet long that I pounded in the ground right outside my house. It's got an acorn nut on the top of it to attach a grounding wire to. (Do a search for "ground rod".) If your house is reasonably modern, you might be able to find a good way to attach it to the ground of your existing electrical system. My apartment is over 50 years old, and its electrical system is not grounded.