I have a light switch at the top of the stairs to the basement. I turn them on and shut the door and listen. I figure the light will send whatever or whoever running for cover or an exit. If I don't hear scurrying, then I switch the lights out.
My intent is to preserve my night vision while hopefully ruining the potential intruder's ability to see as well as me in the dark. Then it's time to go down the stairs with flashlight and pistol in hand.
Now if I'm convinced there is a human intruder, I'm calling 911 and waiting for the cops!