Now I'll give you a real answer.  I have friends in parts of the country where TER and other sources are not useful and BP is their best source.  Used carefully, it's possible.

Make sure you do your research. Always check first to see if there are any reviews.

Somethings that come to mind are.
1. Stolen pictures.
2. Prices way too low.
3. Ads in hot areas with LE activity.
4. Pictures on ads that are way to attractive for the prices.  
5. Real BP providers will know if another BP provider is real. They know each other and some have shared incalls at one time in the past. Ask a BP provider during the session if she knows another provider. You will hear all types of stories, "Oh I got into a fight with her" or "She has pimp".
6. Get to know a hobbyist that you know that is into BP providers and trade info a few times a week.  
7. Quality of the ad, many times text will be all in uppercase and the pictures will not be revealing, although that not always work.  
8. Stay away from providers who share incall or ask you if you want to do doubles when you make an appointment with a BP provider. Best to hang up the phone and see someone else.  
9. Some BP providers will be naked when you come into the room. LE won't be naked, they will be fully clothed. They will try to start talking about prices and services as soon as you get into the room.
10. Stick to ads where the prices are clearly listed in the ads. That keeps down on a lot of drama and discussion about prices.
11. If prices are not listed in the ad, a BP provider will tell you the prices after you make the appointment.  
12. Only see BP providers that are reviewed by reviewers you trust or have a track record.
13. Always search the phone number. If you don't see phone number on previous ads, might be best to avoid until you see there are reviews and a track record of ads.

Well looks like you goofed!

In some areas, Backpage is the best source to find providers. In some areas, it is the only source. I probably wouldn't use it in Vegas with all the other good resources there such as TER. As some of the other replies have said, proper research is essential. There are ways to get good results on BP, and there are some great gals advertising there.