Rob you are right communication is paramount but as Sandra says there are tell tales in body language and appearance. I am a pretty laid back jovial person and get along with most people but when it comes to my dive partner I want to see confidence but not cocky organized but not militant, and somebody who will talk with you not over you. If they are as relaxed as I am on the ride out I feel more comfortable. I like to see someone aware of their surroundings and conscious of the dive site (done some research on the dive site) There are quite a few "used car salespeople" out there that can talk a good game but they can’t hide what their bodies are saying. I am a people reader, as most people telegraph who they are in the 1st 10 minutes of a conversation, if within those 1st moments I can’t find a good footing for a "relationship" I won;t cancel the dive but I will be a bit more apprehensive about the dive with that person. Being confident in my skills is easy but until you are down with someone you can’t gauge their abilities.