I responded to a post of a new provider who was very pleasant on the phone. Said she would meet me in a parking lot then go to her place. Hasn't asked me yet for info to verify me. Should I be suspicious? How do you know if you're being set up for a sting? How often does it happen?

Responded from where? What source? TER? An escort mall? CL?

Meeting in a parking lot is for street hookers. If she is legit, even if she doesn't screen, she will use the standard two call system to get you to her location.  She may not be LE but she probably isn't someone you want to see either.  If she is conducting her business in public it's only a matter of time before she draws attention to herself and that is never a good thing.

She may just be new and not understand the importance of screening. However, I would be very careful meeting someone in a parking lot, especially if she has no reviews.
I doubt that it is LE, they normally set up in a hotel room but you never know. Just watch out for the pimp hiding around the corner.
Hopefully she is on the up and up but be careful, just in case.

There was this one provider in NOVA that met you in a parking lot. I won't mention her name because she has recently retired but she had plenty of reviews. But for the most part, just stick with well reviews ladies and you can't go wrong.

someone that careless cannot be trusted sting or no sting.

might not be LE but it could be Queedo waiting around the corner.

If the lady has reviews, do the reviews speak of this unusual beginning?  Have you PM'd any of the reviewers to ask if this is her standard MO?

Some Providers are Newbies too.  I was fortunate to find one who is now a Fav.  But lax methods are risky & can cause her a boat load of grief as well as anyone who is with her at that moment.  
I have met a young lady outside a coffee shop & then drove to her place in my car...  but I'd seen her before.  I saw her a few times over the three years & each time was a different appartment within the same neighborhood.
As a Newbie, I'd not do this as it differs from established methods...  with a bit more experience, I might TOFTT, with my spidey senses on high.
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YES. Skip this one.