Sometimes I seem to have brain lock for a few minutes and forget which is which. My mom told me that when I was little, I showed ambidextrous tendencies but at the time, doctors were trying to get parents to 'train' it out of you. So, maybe I should have been ambidextrous and that's why I forget. Anyway, this is my trick. Hold your hands out in front of you with your flattened palms facing away and your thumbs pointed toward each other. The hand that forms an "L" with the thumb and first finger is your left.