Open the door that you need hardware for.
Stand in the doorway with your back to the hinges. See Illustration Below (You will be standing sideways in the opening, looking at the part of the opening where the door latches into place when closed).
When you reach for the handle which hand would you use (without crossing your hand over your body). Which side of is the door/handle on? If the door/handle is on your right hand side, it is a right handed door. If the door/handle is on your left side, it is a left handed door - PLEASE READ EXCEPTIONS.
EXCEPTION - If your door swings out into a hallway or out of the home, you will need to order an outswing handing as the lock will be on the wrong side. The best way to determine if your door handing needs to ordered as an outswing is to stand inside the room where the door is located with the door shut. Turn and face the closed door, can you see the hinges? If you can see the hinges, the door is normal swing. If you cannont see the hinges then you will need to order an outswing handing. See an example in the tips below.

Notice on the left hand side, that the hinges are visable with the door shut.	The above door has no hinges visable with the door closed.