I have been working with children since I was fourteen and landed a job with a local youth services bureau in Ottawa. Since then I have worked with them in recreational and social work settings, have taught them, counseled them, performed for them as a family comedian for over a decade, and I've shot them. Many of them. Though I am careful who I reveal that last bit to.

I have a fascination with photographing children. They represent what is best about us, before we grow and become self-conscious and lose our imaginations and sense of play. At our best we retain that child-likeness, but I suspect our love for childhood has something to do with nostalgia over what we've lost. Nostalgia is powerful and images that harness that nostalgia are among the most compelling and universal images. It's not easy to shoot kids, and there are some technical, relational and paranoia-related issues that eventually surface for anyone who wants to point the lens childward.

Children are easy to capture if you approach it right. If you approach your session, or your brief moment, with a sense of play and low expectations, you will be rewarded with the best kind of images of children - ones that are spontaneous and playful and reveal the real spirit of the child. Children can go from laughter to tears in an increment of time so small science has yet to measure it. If you are prepared for this you can capture a range of true emotions that you will never get from a suspecting adult. Here are some of my suggestions.

1. Keep it playful. Let them see the image on the back if you shoot digital. Playing hide-and-seek behind the camera works well. Shooting in continuous or burst mode will allow you to capture the pose and the moment they relax and react. It is that post-snap reaction that most often reveals the true character of a child in that moment. Let kids be kids. Think of the photograph as a collaboration between you and the child - you bring the expertise and the camera; they bring the fun, the unexpected, and the spontaneity.
2. Don't be afraid to use a wide-angle lens for portraits of kids. Get close and wide and capture their face with something in the background that reveals something of their world. Or capture a piece of the firetruck in the boy's hand, or the (stereotype approaching) doll in the little girl's hand. Those details need not be in focus, don't be afraid to shoot wide open at f/1.8 or f/2 - or as wide as you can go. The smaller the number, the less that's in focus. And that creates a nice soft look that is very consistent with childhood (sadly, not always).
3. Be creative about your angle. Shoot from above them while they look up creates an implied relationship of trust or smallness. Shooting from ground level while they are on the ground gives you an insight into how they see the world.
4. If you're using flash take the time to learn to use it well. Flash can be harsh and often ruins what would otherwise be a great shot. Children learn to anticipate a flash and their face shows that anticipation, removing the spontaneous look. If you must use it, soften it up with a diffuser.
5. No matter what else you do, keep the eyes in focus. Most of the time. I have a picture of a niece of mine that has her face very soft and out of focus, with only her fingers and her overly-large cookie in focus. I shot many pictures of her that day but none revealed her character more than the cookie-shot. But when the face is the subject of the image - aim for the eyes. Or in the case of a three-quarter face shot, one of them - usually the foremost eye.
6. Don't be afraid to include props, especially if you're shooting your own kids. Their favourite toy will be a part of your memories. My mother has pictures of me with a teddy bear I kept until I gave it to a niece only a few years ago. Those photographs are some of my mother's favourites, and mine as well. So what if the blanky or the binky or whatever you call it is smelly - it's important to them and capturing that relationship will result in a more meaningful image.

Over the years I have photographed many children with whom I have no prior relationship. This makes me a stranger to them - which adds a new dynamic to deal with - and a stranger to their parents - which adds an element of paranoia, and possible legalities. Let me suggest a couple things. 

1. Learn a magic trick or a corny joke. Much of my photography is in countries where english is not spoken primarily. So a magic trick or two breaks the language barrier. Then I snap a picture of them and show them the back. Usually this results in a posing frenzy, but if you have the patience to wait it out (you can delete them later) you will eventually be rewarded with some candid images.
2. Don't lurk or shoot images in a way that can be perceived as predatory. Be open about this. If you look like you're nervous and have something to hide every responsible adult within sight will be nervous. Engage adults, show them the pictures. Be very sensitive to the parents' rights to protect their children. Remember that the rights and safety of children is more fundamental than your right to photograph them. Photographers who appear predatory in any way will give parents more reason for their fears and will make it even harder for photographers to create meaningful and beautiful images of children without arousing suspicion, fear and hostility.
3. I carry business cards and when it is appropriate - sometimes before I shoot, sometimes after (I take my cues from the context) - I make sure the parents get a couple cards. I let them know who I am and tell them I appreciated interacting with their child and what a great kid he/she is. I ask them to email me with their email or mailing address and I ask them permission to send them some photographs as a thank you. The more open you are with people the more they will trust you.

Photographing children can be deeply rewarding. Be patient, be gentle, be prepared for anything, and shoot with your heart as well as your camera.