You primary criteria should be to see providers who are well reviewed. Since you're skittish, let other guys confirm her legitimacy. It's also a bad sign if you're contacting her anonymously and she doesn't ask for any screening info and/or is explicit in cost per sexual services. Any action that exhibits carelessness on her part is a red flag. LE wants to make it as easy as possible to get you in the room.
I also don't know why "avoid if you can't see their face" is on your list. Showing her face is a bigger danger since it makes her easily identifiable. "Partially nude in the pics" is irrelevant.I know to avoid ads with party and ads without any Google history. I've actually gotten very cautious which has ruled out just about 99 percent of providers. If someone doesn't have a bunch of recent reviews, I tend to avoid but am I being too cautious?
You see the same girls posting on BP daily but yet they have no reviews. Is there LE concern if they post so often? I would think LE would post something that has no trail. Have they ever used an established providers profile w a different number?
Here is what I avoid: avoid if they say Party, avoid if they say they are 18, avoid if you can't see their face, avoid if they aren't at least partially nude in the pics, avoid if no reviews.... am I too extreme
You primary criteria should be to see providers who are well reviewed. Since you're skittish, let other guys confirm her legitimacy. It's also a bad sign if you're contacting her anonymously and she doesn't ask for any screening info and/or is explicit in cost per sexual services. Any action that exhibits carelessness on her part is a red flag. LE wants to make it as easy as possible to get you in the room.
I also don't know why "avoid if you can't see their face" is on your list. Showing her face is a bigger danger since it makes her easily identifiable. "Partially nude in the pics" is irrelevant.
I am sure my reasoning is off but if the picture matches the ad there is some nudity, I figure an LE wouldn't want naked pictures of them out there, while a girl who has comitted to the craft wouldn't mind.
Yup, I know lots of recent reviews is the way to go but so many girls don't seem to have them. And I've even noticed some girls who had them now dont. Not sure how or why.
But I would think logically if someone posts almost every day, that can't be LE, right? Most of the Asian ads are like that and I would guess newer girls are like that too... is trying some of these just too much of a risk?
Also, upsells and poor performers. You should be able to cross reference the legit providers on BP and just beware of ads that seem too good to be true (ex. super hot, bargain-priced). In general, you get what you pay for. Avoid the cheap specials, and turn around if you find yourself at a motel with rooms that open to the parking lot.
Out of curiosity, why do you avoid motels with doors opening to the parking lot?
BP in itself is not the problem, nor is meeting at a motel. The one thing all newbies should avoid is any woman without reviews. We can argue about how many reviews makes a woman "well reviewed", but the one thing we can all agree on is that no newbie should be TOFTTing. Personally I don't go so much by how many reviews a woman has, but how credible the reviewers themselves are. One or two reviews from guys I know are worth a lot more than a dozen reviews by first time reviewers or other mainly unknown guys.
It's a very good question, but you are essentially asking "how safe is safe?". That will come down to your comfort level. Playing in this space involves some risk - minimizing that risk is what TER (and doing your homework) is all about. Some guys like finding hidden gems and the significant risk/reward involved - others like to stick to tried and true providers.
My days of TOFTT are over (fingers crossed), so I stick with well reviewed (having at least 10 recent reviews, most of which are not first time reviewers) ladies. I may even pm a recent reviewer to get some more info. Networking is a useful tool as well, when you develop that skill. And you might even make a friend. 
Whether she has ads on BP doesn't really bother me as a general rule. But words like "party friendly" do. Also if she offers quick visits - that's an issue for me. And, of course if her donation is too good to be true - it often is. It often means upsell or lax safety practices.
But that's me, and my rules may or may not work for you. But I do encourage you to do some research (and maybe networking) before you jump into the BP unknown.
It can save you a bunch of heartache later.
Good luck in your search.
Here is what I avoid: avoid if they say Party, avoid if they say they are 18, avoid if you can't see their face, avoid if they aren't at least partially nude in the pics, avoid if no reviews.... am I too extreme?
There are quite a few reputable ladies, who advertise here on the ad boards, who don't show their faces, do not have any nude or semi-nude pics, and may only get new reviews very infrequently.
So perhaps a case-by-case basis would be a more moderate approach?
These ladies obscure their faces and may ask clients not to review them for the same reasons you LOOK for those things: safety & discretion! They are trying to keep a low profile, but in so doing, are apparently casting up red flags in your view.
There is no one simple method, guaranteed to always work, IMO. 
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her pics are hot... and price is too low... it's too good to be true. Run picts through tineye or google image searches.
It's harder now that TER does not allow links to BP... a recent change. Providers change their numbers all the time... makes them harder to keep straight.
Even BP gals get TER reviewed pretty quickly...