If you do not have a light kit, check the switch to see if the black or red is connected to the dimmer switch if there is one. If you have a light kit, there should be two hots, two neutrals.
__________________ Ren: Now listen, Cadet. I've got a job for you. See this button? Ren: Don't touch it! It's the History Eraser button, you fool! Stimpy: So what'll happen? Ren: That's just it. We don't know. Maybe something bad, maybe something good. I guess we'll never know, 'cause you're going to guard it. You won't touch it, will you?