It is traditionally flown either to the right or the left of the front door. It can be on either side. When there is a choice, find a position of prominence. Sometimes that is the left of the door, sometimes the right, sometimes away from the door, but centered on the house (when you have a porch, for example). Use your best judgment to find a nice position for the flag. However, if you fly a second flag, then the US flag must be on the viewer's left of the other flag, as you approach the house.