What he said.
For starters, if I want a massage, I look in the massage section. If want some "stress relief," I look at the body rub ads.
If you're looking at ads where you can't see the lady's face, or she's showing more than she'd show while walking through the mall, or she's wearing lingerie instead of scrubs, chances are she'll provide at least a happy ending. Backpage ads typically have links to other ads posted by the user, and some ladies share an account to post ads from. So if you can't find a review on he lady in question, you might be able to find a review on someone she works with -- though levels and quality of service often vary from lady to lady even at the same location.
Googling the phone number might provide some insight.
My rule of thumb about BP ads for ladies I can't find reviews for: If she's been advertising on BP for at least a couple of months under the same name, chances are she's legit. But then I'd be wondering why there weren't any reviews
If a woman says in her ad that she's not an escort and doesn't do that so don't even ask, a condom almost certainly won't be necessary for your visit. It also doesn't preclude other activities -- but don't assume anything.
Finally, there's quite a bit of difference between a massage with a happy ending and a sensuous non-FS session. Unfortunately, while most bodyrub girls are at least minimally adept at fluid extraction, very few have the interest or skill in making your experience an erotic one.
Happy hunting!