A Problem With My Lamp

You are standing in front of a room with one light bulb inside of it. You cannot see if it is on or off. Outside the room there are 3 switches in the off positions. You may turn the switches any way you want to. You stop turning the switches, enter the room and know which switch controls the light bulb. How?

Okay, I do actually have a real problem with the lamp in my living room: I don't have one. It's very dark in here.