A few things I watch out for when trying to predict the chances of extras:
* Add points if open late in the evening. Deduct points for a strictly 9-5 shop.
* Add points if open seven days a week, small deduction for not doing Sundays.
* Add points if they say that the massage will be by a woman, or they picture women masseuses, small deduction if not (after all, if it's a purely health thing, you don't care if it's a man or woman right, just like most people don't really care if their GP is male or female).
* Obviously add/deduct a lot of point if someone tips you off as to their result
I've not had a false positive except for one place in the USA, where I wasn't sure of the guidelines/law/etc.
I guess there may have been false negatives that I wouldn't know about (places I thought wouldn't do it, so I didn't go, but in fact they would)
