Everyone is unique. Pardon me if I have said that already for the 1000th time. But this is the single most valuable, and obvious, lesson I have learnt while photographing people. Every one has a trigger that either makes them happy or sad. When creating the photos I'm generally trying to find that balance where I can quickly turn them into a glowing face to something serious if the photo demands it. Identifying that trigger is a task photographer needs to complete. It's easier when the subject is a friend but a totally different task when it's someone you aren't familiar with much or a complete stranger. Some times we know someone or we think we know them so well that we unknowingly keep activating those triggers. In these shoots, starting a conversation is a crucial process to identify that trigger. What gets them excited, what gets them wanting to talk more, what shuts them off, what shuts you off from them (when someone shuts you off, you've probably failed. But learn from it and move on). Damn, it sounds easy when in theory.