How to greet a patient?

We doctors meet large number of patients everyday. How should a doctor greet a patient?
Different doctors greet patients differently. It may depend on many things. How busy a doctor is may be one of the important factor. Also, the local custom play a role.

How do I greet my patients? I never open the door for my patients. Either the nurse ushers them in or they come in by their own. I will be sitting at my desk and nodding my head with a smile. Then I will start the interview asking How are you? or what happened? or what is the problem?
If I am too busy, I may be taking down some notes of the previous patient or attending a telephone call in between patients. Then, I may look at the patient's face only after he/she is seated. May be it is rude but.....
How your doctor greet you? How would you like to be greeted by your doctor? Comments and suggestions are welcome