"Smile!" but look at me.
When on assignment I am sent with specific requirements on what ideas the images are supposed to convey, as well as look and feel. "Oh, and make sure there is room for type! but not sure of exactly where it will go." So as random as it feels sometimes, I get mandates like "go photograph pregnant women in India with gestational diabetes." One of the most important aspects is authenticity. Keeping the images "real" is probably the biggest challenge. Its much easier when things are planned and working with models. You can control the look and the feel of the images that way. Although that can have its pitfalls when it comes to looking authentic. Working with real people it can be hit or miss, of course being a professional it is expected that there is more hit than miss. You can tell people stand there and look this way, and that way, but how do you convey an idea you want them to express in their faces and body language? This becomes particularly problematic with cultural and language barriers. Many times I show up at a persons home in a rural area of another country that is off the grid like an alien from another planet that just got off a spaceship. Although my visit is usually pre-arranged. Most people have no clue about, why am I there, what I am doing, why am doing it, why is it important, and what is the point of it all. Not to mention I am probably the first foreigner that they have ever seen up close let alone interacted with, and a man no less which can be an issue in very conservative countries. Also I want to take lots of photos over here, over there, doing this, doing that....I get 20 minutes tops before people start getting tired of the whole thing. Plus they have work to do!
So whats a photographer to do? Sit down and have tea, share a moment, get to know each other a bit, and do more than hope for the best.