Keep your legs locked. The point of the dance is to look like a sci-fi robot, and they don't have knees. Most people don't walk while doing the robot, but if you do, think '60s space movies.
Bend your arms at the elbow, keep your elbows at your waist, and keep your hands open, as if you're going in for a handshake. For a basic robot dance, extend one arm while bending the other inward. Do not pivot your shoulders; move your arms only at the elbow.
As with the arms and legs, stiffness is the word. But moving your torso requires a little coordination. There's no real rule on how to move, just as long as you're pivoting forward or at an angle along with your arm movements.
For an extra-rickety look, shake your head slightly to make it look as if it's going to fall off. As for the face, people usually go with a blank, wide-eyed stare.
Counting and moving to the beat is useless while you're doing the robot. Robots are not human and therefore are oblivious to the rhythms and emotions of music. Move deliberately out of time and with no distinguishable pattern.
The Robot is a proper dance only because lots of people can do it and lots of people like it. Just keep your movements unpredictable and jerky, and you're good to go.
Though the robot seems like a joke dance, it's actually part of a dancing sub-genre called popping, and its practitioners are dead serious about developing killer moves. If you're tired of doing the same old robot moves, look to the master: Michael Jackson. As with every dance he ever did, Jackson innovated and pushed its limits. Jackson's live duet with R&B star Usher showcases both their talents at doing the robot.