What is the best practices(Tools)( to recognize your guest ?!

At the very first, you should greet the guest courteously. Showing that you are genuine with the things you would say to him or her. Always give him or her the best smile. Remember that first impressions last. So, if you act to the  guest the niciest way, your guest will be approachable. You will recognize your guest if he or she is having a bad mood or what.