Generally, information about the target is programmed into the missile just prior to launch. This can include coordinates, radar measurements (including velocity), or an IR image of the target. After it is fired, the missile guides itself by some combination of gyroscopes and accelerometers, GPS, organic RADAR, and infrared optics. Some systems offer the option of either continued input from the launch platform or fire-and-forget.
"Why don't you be a tiger?": The Performative, Transformative, and Creative Power of the Word in the Universes of Diana Wynne Jones
May 01, 2010; I am knowledge, force That words of power have, science deep In the head, the arrowpoint that's made Exactly for its target,...