Check out the video at http://www.doityourself.com/video/How-to-Repair-a-Blacktop-Driveway-Crack-61996587.
In summary, use an Asphalt Repair compound (see here at Lowes) with a Caulking Gun, insert small stones where the crack is a bit wide and cover the whole crack with some sand (from the side of the driveway) to mask it and to avoid getting stuck to the underside of shoes, when still wet.