What not to do when greeting customers?

As a professional in the cryptocurrency and finance industry, I'm curious to know what mistakes should be avoided when greeting customers? Is it important to maintain a professional yet approachable demeanor? Should we avoid any specific phrases or body language that could be perceived as rude or dismissive? I'd like to understand the dos and don'ts of greeting clients in this field to ensure that we're always making a positive impression and fostering a strong relationship with them.