17 out of 20. I labeled one genuine smile fake (eleventh person - I remember I wasn't sure about this one). And I marked two fakes smiles as genuine. I wasn't sure about them either, but in their case I was actually trying to be considerate. Maybe those are shy smiles, I thought. Lol :D
I guess I've got pretty good results. I look for the eyes and for overall feeling. If smile is genuine, it makes me smile back.
*smiles*