How do you throw a rock as far as you can with no strings attached and nothing on the person or the rock?

If you're asking what is the optimal angle at which to throw it... on a flat surface and ignoring air resistance you can optimize the distance traveled by throwing it at a 45 degree angle to the ground. Since the earth is actually curved, you can do a bit better by throwing it at a very slightly flatter angle; the precise angle depends on the speed. If you could throw it at 5 miles per second or so, the optimum angle would be parallel to the ground, since that would be sufficient to put it into orbit (remember, we're ignoring air resistance).