"Smile for the camera!" always causes a cheesy grin. Asking him to "Say cheese" produces a constipated look. How do other parents get their kids to look so natural in their photos? You want your pictures to capture your child's real self, not this fake face. Try some different tactics to get the look you really want.
Ditch the idea of posed portraits. Sitting stiffly while a photographer tells you to smile is a surefire recipe for a fake expression. That's why your child's school photos all look so strained. Instead of taking photos where everyone is looking directly at the camera, ask the photographer to take pictures while you are talking and laughing with each other. Action shots are more likely to show real smiles.
Say something silly. If you want a real smile from your child, you have to do something that's real smile-worthy. Younger children might smile for silly sounds, and older preschoolers will almost always smile for a good fart joke.
Instruct your child not to smile. You know the drill. You say, "Don't bother your sister," and the first thing he does is bother his sister. Children are often contrary, and when you tell your child to do something unexpected like not smiling for the camera, he's likely to flash a real one.
Snap fast. The precious moments go by in a flash, and if your camera flashes three times when you push the button to avoid red eye, you're going to miss the moment. Always be ready to snap the picture. In many digital cameras, pushing the picture button halfway prepares the camera for the picture and allows the camera to take the picture quickly when you finally push it all the way.
Use the "continuous photo" option. Some advanced cameras have an option for taking several photos in succession. This allows you to take hundreds of pictures in a short period of time. When the kids are asleep, you can wade through all of the shots to find the one good one.