void Update ()
{
    transform.Rotate (0,0,50*Time.deltaTime); //rotates 50 degrees per second around z axis
}

take a look at link texttransform class and it's methods

There is a script ready in case of Lerpz which can be downloaded directly from the official site. Is the tutorial 3dplatform

var degreesPerSecond : float = 50.0;

function Update() { transform.Rotate(Vector3.up * degreesPerSecond * Time.deltaTime, Space.Self); transform.Rotate(Vector3.left* degreesPerSecond * Time.deltaTime,Space.Self);

rigidbody.isKinematic = true;

}

you can use this one also to rotate constant speed as u want.