One tell-tale sign is probably someone who has zero reviews.  Have you any reviews LOL?

As far as a MAN getting set-up or busted, cops tend to like to control the environment in which they make arrests.  So doing outcall with a reputable provider is your best bet.  

Look for the following tell-tale signs:

They ask you to describe precisely what you "want" for your money.  They go out of their way to EXPLAIN what you'll get in exchange for the money, etc, even if you do not ask.  They'll try to be explicit, as that makes for an easier conviction.  You'll also often hear weird clicks or noises on the phone line.  A situation that is likely to be "legit" is one where the girl describes nothing on the phone, not even money.  No noises on the phone. She appears to not be nervous, etc.  She will not try to get you tslking more, and will say very little to you.

Incalls located in motels are more likely to be a sting than in private apartments.  Why?  Cops would need to rent an apartment otherwise.  They can rent a motel room for cheap. If directed to a motel, they'll often have you go to the parking lot and identify your car, this way they can often stop you in your car, without ever setting foot in a room.  Depends on what was said on the phone.

When in the room, run if she starts discussing money or donations. Never reference the cash at all.  Do not display it to her.  Just be quiet.