How to handle a client driven with hysterical behavior during an appointment?

First and foremost, you should keep calm.  Do not counter his hysterical behavior with similar emotion.

Listen to what he has to say.

Then, explain to him in a polite manner why you cannot give in to what he wants - that is, immediate attention.

If he persists, be firm and stand on your decision with authority. This is now the time to let him know that the customer is not always right (but again, say it in a polite manner).

Do not argue with him/her unless he address a direct question, try to listen to him and stay calm as long as you can, look straight in to his/her eyes and show that you totally understand what he/she is saying or complaining about, promise him/her that you will personally take care of his/her problem, give him/her a direct line for you in case anything happens in the future.

just be quite,donot interupt him,donot show any agressive body language gestures,just let him scream,talk until he is done,when done offrer him a glass of water ,then ask him the following..sir,we have listeneed to you can you please allow me to help?i am here to help you,what seems to be the problem....etc.

it works evrytime.

First listen to what the customer is saying and pay attention regardless of whether the customer vis shouting or acting that way you make the guest feel relieved and assured he is in the right hands, give the guest time to relieve everything from inside, apologize and assure the guest you'll sort all the problem soonest possible, right away solve whatever you can there n then and if there is an alternative to the problem address it there, after the guest seems satisfied and back to normal thank the guest and welcome them again make sure you see off the guest, it makes tgem feel part of that environment and be assured they wil come back for more. Remember even if they didn't apologize there they are satisfied and sooner or later they wil come to apologize

ook straight in to his/her eyes and show that you totally 

first thing to do is listening to him and let him believe that he is right and avoid showing negative attitude toward him and finally i will offer him a drink. ^-^