I've answered this question many times in many ways but have never been truly satisfied with my answers or felt they were completely informed, researched and stamped with the Good Housekeeping Seal of Approval. Things like that bug me to no end-I'm supposed to know these things! Don't ask yourself that question, though. Don't ask what your own most common rough spots are. Don't do it. I'm warning you; it's a dead end. The apparent number of answers is ... aw, just Google it.