Hold your scissors like you're cutting something. The top blade should be on the right side and the bottom edge that whatever you're cutting rests on will be on the left facing you. This is true even if flipped.

It would be reversed on left handed scissors. This is the important difference. It's more common nowadays for the grips to be ambidextrous, but the blade is still an issue. Of course lefties CAN cut things with righty scissors. But try out a lefty pair sometime. You'll find the blade blocks your view of what you're doing. You can't easily see the line that you're cutting.