spawn random object and move it

I need help with scripting on how to spawn a cube at a random position (In 3d) … say its a falling object.
And how could you make this as efficient as possible?? :smiley:

float x = Random.Range (-10, 10);
float y = Random.Range (-10, 10);
float z = Random.Range (-10, 10);
Instantiate (somePrefab, new Vector3 (x, y, z), Quaternion.identity);