I feel Im very careful but what will be tips that one may be le? for you really have no way in knowing until it's too late.

There's no sure fire way to know for sure. Acting oddly perhaps. You must use your gut.

LE uses moles and informers mostly so its hard to tell who LE Might be.

If you do your research here on TER, stick with well reviewed and established ladies who conduct their business with discretion, and act with discretion yourself, you will have little to worry about.

If any provider ever starts trying to get you to get specific about what you are paying for, walk, no RUN to the nearest exit.  Generally speaking, the crime is the solicitation of sex for money.  Never, ever, under any circumstances say anything that boils down to 'I'm offering you $X00.00 for fucking and/or a blow job.'  
Read the lady's reviews, find one that does what you want, contact her and make an appointment to 'spend an hour with her'.  Provide the lady's 'gift' discretely as she instructs (the good old white envelope left in the bathroom or on the coffee table).  
If everything fails and suddenly you are confronted by cops, admit NOTHING, ask for a lawyer.  Do not believe that you are going to talk your way out of a bust by 'cooperating.'  
MVR

get VIP so you can read the details in the reviews.  The better informed you are, the more likely you will have a great experience.

Its probably NOT a good idea to say huh ?

At what point after you meet and give the donation is it safe to say anything?  I've read that some encounters involve small talk/conversation beforehand.  What if the provider starts to bring up do's and don'ts before any type of physical contact?

Small talk...... as long as there is NO pairing of the money and any sex act.  That would include her asking you want you wanted right after you laid down the envelope!!!  Were that to happen, I would say something like... gee... I don't want anything... I just came here to bring you a gift and hang out with you for awhile!!!  
Accept the fact that until she has sucked your dick or fucked you the first time, you cannot be 100% sure she is not LE.  No female LE is going to suck a cock or fuck a guy to get a simple soliciting bust.  After that, its pretty much golden which is why when you find a good provider, you go back rather than go through the hassle of establishing with another.
MVR