This can be done one of two ways. If you live in an area where kids go to bed at a decent hour, open up all your curtains, shades and blinds late one night, turn on all the lights and freak the hell out of each other. I know it sounds silly but the mere thought that someone "might" be watching can be a fantastic turn-on. The other way it can be done is to fuck each other in a house full of people while taking the risk that someone might walk in on you. This can be very exhilarating at holiday dinners where some old-fashioned relatives might catch you getting busy.