Not only check her reviews, but when she starts taking off her clothes as soon as your get to her place, then I'd say 100 percent she's not a cop.
When meeting a provider for the first time, say in a hotel room of her incall, is there a specific time/action that reveals she is legit? For example, if she greets you in panties and a bra, is that something a sting cop could wear? Can someone detail the first moments, to stay out of trouble? Might sound stupid, but as a newbie, I haven't "been there, done that"
It's either cool, or it's not. Only you can make that determination, as things are happening real time. In my experience, I've never had to bail, and that dates back to '04
...alone in a hotel room. Everything will be recorded on video. Her backup will be in an adjoining room. She will try to get you to talk about sex in exchange for money. She may say something like: "What do you like?" or "what are you interest in doing?" She'll also probably ask if you'll be okay with wearing a condom. This is to make sure you can't claim you just wanted a massage. As soon as you put the donation down, she'll signal the cops in the next room; they'll bust in and bust you.
There's still a double standard with undercover cops. Male cops will allow a provider to do an LE check - she can grab his junk - and they won't care. Some male cops will even have sex with a provider and still bust her. But female cops won't do anything more than give you a hug. They'll also be dressed more conservatively - no bra and panties. They don't want the trick to claim entrapment.
To be safe just don't mention sexual acts in exchange for money. If she's a real provider, you both know what you're there for, nothing needs to be said. Say your hellos, make some small talk and get busy. If she tries to get you to mention sex for money before her clothes come off - get out if you can
Not only check her reviews, but when she starts taking off her clothes as soon as your get to her place, then I'd say 100 percent she's not a cop.
If she has a page or more of good reviews, then the likelihood of her being LE is effectively nil.
On the other hand, if she is just a BP ad with no reviews, it is a crap shoot at best.
LE can do just about anything it wants. Being in a courtroom trying to win a case claiming entrapment is not what I call a successful outcome, even if the judge does toss the case.
Certainly as a newbie, you need to stay far away from the dangerous side of things. Maybe after some years and you develop some "Spidey sense", you'll be able to play the BP game, but till then, play safe
When you leave the room and are not wearing bracelets.
Then look at reviews. Pick a provider that has at least several reviews and click on a reviewers name. This will show you how many reviews he has. A lady that has a number of reviews by guys that each have reviewed a fair number of gals is almost certainly legit. Enjoy!
....if nobody barges in with badges and weapons drawn, other than that threre is no effective LE check despite what you may read in reviews. You shouldn't need to be worried about an encounter with LE if you have researched your companion well, before settling up the date. See only ladies who have a history of good reviews by guys who have a long history of writing reviews and you should be relatively safe from the many things that can go wrong besides meeting LE.
The best thing you can do for yourself if you stumble into a LE sting is know your rights. Lying to LE is a crime you never have to worry about committing if you exercise your right to remain silent, speaking to LE can only dig your hole deeper. Don't make excuses, don't try to explain, don't try to talk your way out of it, just shut your mouth.
Never ask about sex or talk about condoms or try to use code words when setting up your date. Doing that is a good way to get ignored by a provider or you could be giving LE a lot of good evidence if you're talking to them while they tempt you into their net.
Know as much as you can about who you are going to meet and don't be fooled by an unscrupulous provider using stolen pictures to lure you in and steal your money or worse. If you do your homework before meeting someone you'll walk out with a big smile on your face wondering why you didn't do it sooner. If you don't do your homework you make walk away wondering what in hell you were thinking.
...once her mouth is wrapped around you, it's generally a pretty good indicator that you will not be arrested. 
Until then, if I am ever unsure, I just wait for her to make the first move. If she is legit, she will.
As others have said, if you stick with recently well-reviewed ladies, you will be okay. P411 makes this a lot safer also -- join!
Also, be sure to make sure that the images on the site are the same as the lady you meet. There have been (a few) cases where LE either busts and turns an escort OR somehow takes over and uses an old website. So if you arrive (or she does) and the lady is not the one you expect, just tell her that you don't like to be baited and switched so you are not interested in continuing with your therapeutic massage -- and walk away. You might have been wrong, but why risk it if you don't feel comfortable. But again, THIS is why it's best to stick with well-reviewed ladies. And don't forget, the purpose is to have fun!
This is how I think, but I could be wrong. Never talk about money. You're on a date, you've met a girl on the Internet and you're ready to hookup. Her website should say something like donations are for time only and not put price points next to sex acts. Don't email or ask over the phone about what she will do. Ask what she enjoys, what's her ideal date if you must. But read her reviews to see what she actually does.
Once you're in the room say nothing about money. People have hookups all the time and if you want to help cover the hotel room then you're a gentleman. Make sure she puts the security bar on the door and there's no adjoining room. I think when her mouth is wrapped around your cock you can relax.
Also, if everything goes to hell and police barge in follow everyone's advice and stfu. Ask one question - am I under arrest? If no, leave. If yes, say I want a lawyer and stop talking. They will be pissed because they hate lawyers and you've just become a pain in the ass. They will try to get you to start talking again, because if you do that it's an implicit waiver of your right to counsel. Tell them you want a lawyer and stop talking.
Just my random thoughts, not legal advice.
LE will never send a lady to unknown environment. LE almost always uses a low end motel room with adjoining room. Their budget doesn't allowed them to setup in a high end hotel. Drive around the motel and look for anything odd.
Either do an outcall or pick a lady who stays at a higher rated hotel. Check out her reviews. Even without VIP. You can see if a lady is legit if she has a lot of reviews by reviewers who has written a ton of reviews. If you want to you can check your local board. If a lady is active on the boards she isn't LE. If a reviewer posted a lot on the boards then he isn't LE. LE doesn't have time to after the TER boards. They target people who don't know what they are doing.
LE basically only do the motel setup like the ones you see on "Cops"