Turn the lamp off by its switch and tighten the bulb. A flickering bulb may simply be the result of a loose connection at the point where the bulb connects with the lamp.
Unplug the lamp and plug it back in to a different outlet. If your circuit has too much voltage running through it, then your lamp may flicker.
Unplug the lamp and leave it unplugged. Take the light bulb out and set it aside. Insert a flathead screwdriver beneath the tab that the light bulb connects to. If this tab is not touching the bulb, then the lamp may flicker. Bend the tab up about 1/8 to 1/4 of an inch. Replace the light bulb and plug the lamp back in. Turn it on to see if the flickering has stopped.
Unplug the lamp and remove the light bulb. Brush out any dirt, dust or rust from the socket area with a wire brush. Replace the bulb and plug the lamp back in. Turn it on to see if the flickering has stopped.
Unplug the lamp and examine the cord for any frays or tears. If you find one, cut the wire on both sides of the frayed area. Remove the frayed part of the cord completely. Strip both ends of the wires (the side that's connected to the lamp and the side that plugs into the wall) with a wire stripper. Insert the stripped ends of the wires into a wire butt splice. Crimp the splice down with wire crimpers. Plug your lamp back in and turn it on. If the flickering still hasn't stopped, call an electrician. You may have a bigger electrical problem on your hands.