That's a very practical question! The best way to hang Christmas lights on rain gutters is to use clips or hooks specifically designed for this purpose. You'll want to make sure that the hooks are attached securely and that the lights are evenly spaced out. It's also important to choose lights that are weatherproof and designed to withstand the elements. Make sure to read the instructions carefully and follow any safety guidelines to avoid any accidents or injuries. Have a great holiday season!