Expressions are by far my favorite challenge with my subjects, especially children, you never know what they are capable of until you get them in front of the camera. Some are oblivious to your presence, while others are shy, and there are those that will blow you away with some of the images you manage to capture. Naturally the more relaxed the subject the better the facial expressions. Cheesy staged smiles have never appealed to me, I like natural facial expressions. Trying to get these expressions seem to come easier if you know what your subject likes, such as video games, sports, whatever their interests its best to find this out and get them talking, I have found this is when I get my best expressions and they never notice I am clicking the shutter. Have fun, take your time, always be set up and ready before they arrive, no distractions.