Unfortunately there is no hmd calibration notification but Greg has included a audio feedback. When i do calibration i do 3 standing first in different locations and do a half-crouch for the last two. Make sure you are facing your kinect when calibrating as it can effect you hip position. Is there any natural light getting into your room? (I found this to effect tracking for me) What body part do you think the height of the kinect is around? (Chin height is the best)
Edit: When I do the standing calibration I stand in t-pose looking at around where the kinect is. (For the height of the kinect i actually use my gpu box to raise the height of it so it is around my chin height.)
Edit 2: The trial period lasts for 7 days but only for 10 minute intervals. I found this frustrating too as calibration was an issue for me too.