If you still decided to book her, then it's also important to try to understand her personality in the first minutes of seeing her before you pull out your cash. If she has a mean look, rude tone and generally not friendly enough, then just turn around and walk away. Otherwise your chance of being scammed is very high, just don't risk your money (and hence your mood for the rest of the day or more...). This is all in case of an incall. I suggest not to invite outcalls altogether unless it's a reputed agency.