How to smile??

i realised that during every photo session i had, friends and camera man would blurted out 2 me, 'hey you, smile please!'. but geeZ, i dunno how 2 smile very well. and its kinda funny that even my sony cybershot with smile detection wont detect and capture my smile. i would say **** camera, ****** camera! it was as if im not smiling at all! how to smile then??!!