the #1 way to know if the ad is fake is if they show their face, especially if they're hot. think about it, why would you show your face when advertising yourself as an escort. imagine you go out into a mall and you get recognized. also if they look like a supermodel and all the pics are of different clothes - 99% its photos taken from instagram.
often times i found legit postings usually hide the face either by camera angle or an emoji, and are all in the same clothes, cus these girls are too lazy to put on different outfits. also if they're all in the same room/same bed, its probably legit