#1 Make it fun. This is probably the most important thing if you want natural looking faces looking back at you from the photos. If you're lucky enough to have the weather for going outdoors, do so. Go to a place that's fun and engaging, such as a wood, or a beach. Pretty much any place that your children enjoy would work, but try to be sensible about mud and puddles, or at least save them for the end. I like being a fly on the wall and just work around whatever entertains the kids most and keeping any posing to a minimum.
#2 Keep conversation flowing. This one can be tricky if you're trying to concentrate on the lighting/camera settings/etc but kids feel most at ease if you genuinely interact with them and keeping the conversation going. Ask open ended question that encourage them to tell you about their interests or hobbies, pay attention to what they say and respond instead of keeping your answers brief.
#3 Don't force those smiles. Neutral faces look so much better than begrudging smiles. Always. But if you must have a smile, then I find that most genuine ones come straight after a good giggle. Keep that in mind and your snapping finger at the ready as you're trying to come up with something funny. No pressure there. Better still, ask them to tell you a joke, that works just fine too.
Enjoy the outtakes from our latest *still nameless* cardi shoot.