Remove pets and people from the room. It may seem helpful to have a number of bodies on hand to herd the bird out, but that can actually overwhelm the small animal and immobilize it with fright.
Open one window in the basement and cover the rest with heavy towels or blankets. Turn all lights off to leave the room as dark as possible and stand quietly for a few minutes to allow the bird to become acclimated to the dark. Most birds will fly toward the bright light outdoors and will escape without much trouble. If this method fails, proceed to Step 3.
Crumble a piece of bread and place it in the center of the room if your basement does not have windows. Leave the lights off and shine a flashlight directly on the bread. The smell of the bread will attract the bird, and it will stand still for a minute or two to feed.
Toss an open mesh net over the bird. Walk slowly toward the net, picking the bird up gently with the net still around it. Take the bird upstairs and outside, then carefully lift the net off the bird. Open your hands and allow the bird to fly away.