Basic options. A flag not flown from a pole can be hung from a wall and even over a window, according to the U.S. Flag Code. From the perspective of an observer on the street, the stars should be in the upper left whether the flag is hung horizontally or vertically.
No-nos. Never tie a flag to a tree or drape it over a car or boat. Such displays are considered disrespectful.
Nighttime rules. A flag flown outside at night should always be illuminated. If that’s not possible, take the flag down at sunset and fold it away neatly.
Maintain appearances. The worst offense in flag etiquette is flying a worn-out flag. If a flag is faded or tattered, it should be burned ceremoniously, believe it or not. Your local American Legion office will incinerate it for you if you ask.
Source: Real Simple