I keep reading on TER about getting the standard "LE check" out of the way at the beginning of the date.  I assume it is to verify that either of us aren't law enforcement.  What excactly is it?  A series of questions?

there is no check to safely rule out LE for either party. What it means is that both you and the girl grope each other's privates, because supposedly, a cop or a decoy isn't allowed to do that. Wrong! They can do basically anything they want and still arrest you.

So, don't believe anybody who says you can go to an incall you're not sure about and just walk away if she fails the LE check. Her backup will handcuff you before you know what hit you.

On the other hand, if a provider wants to go though an LE check with you, just play along if it gives her a false sense of security. There's no harm, maybe even a little pleasure.