This has been covered a few times, but here's a summary:
1. If the rate is listed at 200 or less, it's usually a fake. If it says 50 an hour it's always a fake.
2. If the ad is listed in many places within the region, over and over, it's a fake.
3. If the stats make no sense, like 7 feet tall or 68 pounds, it's a fake.
4. If the ad says asian and it's a pic of a black, white or other girl, it's a fake.
5. If it says she supplies party favours, stay away
6. If there are no reviews of her, be careful
7. If it lists anything more than email and a text number, signal, telegram or both, kik and other ones especially if there's a lot of them, it's a fake
8. If you can find the same ad in other cities, it's a fake
9. If the only contact is OF, it's a fake.
10. If they demand a deposit immediately, and there's no reviews of her, steer clear.
11. If it says fuck me and record it, looking for a boyfriend, or other stupid come on line, especially when there's some or all of the above as well, it's a fake.
12. If they are looking for help, or posting a screen shot trying to convince you they are a student, it's fake.
13. If it's after midnight and they are outcall, be very careful. Many of the late night outcalls are scams, they will take the money and run.
14. If the ad title says incall/outcall/facetime it's usually a fake.
15. If the ad pics look like she's more likely to be found on the street than on the internet, pay attention to that, especially if she's talking about partying. Double that if there's a crack pipe visible
16. If you recognize the girl in the ad as a pornstar, it's 99% likely to be a fake. Haley Spades or Kali Roses or whoever isn't turning tricks for 300 in Vancouver. Ever.
17. If the pics are found on tineye, google reverse image search/lens it's fake too.
18. If her only reviews are posted in her ad, text messages or from a certain board east of here, that isn't TERB or MERB, be careful
Hopefully that gives you something to work from. If you have any doubts at all, it might be worth it to keep looking. It's not an exhaustive list, YMMV and sometimes there are diamonds in the rough, but always buyer beware.
Whatever happens, post about it here and let others know what happened.