From Military.com
Quick list of Flag Etiquette Don’ts:
Don’t dip the U.S. Flag for any person, flag, or vessel.
Don’t let the flag touch the ground.
Don’t fly flag upside down unless there is an emergency.
Don’t carry the flag flat, or carry things in it.
Don’t use the flag as clothing.
Don’t store the flag where it can get dirty.
Don’t use it as a cover.
Don’t fasten it or tie it back. Always allow it to fall free.
Don’t draw on, or otherwise mark the flag.
Don’t use the flag for decoration or as a prop.