It's a minefield, but as some others have hinted at, in a good way, ie, the "WSWS?" hunt seems to be addictive. I've been going to these places for some years now, and I've got only a few tips, but mine would be:
If the price is low, eg, £40 p/hr, then extras are likely, as they couldn't make a living on that. Conversely if they advertise, say, £80p/hr and you pay up front without any assurances, you're a hostage to fortune.
Also, many "legit" places I've been to have a strict manageress, but the girls' attitudes vary enormously, and I've had owo or FS many times at these places, but clearly no assurances, and enquiring in advance is almost a guarantee of failure.
If it's not been discussed in advance but you get early swipes etc, then you're usually onto a winner, even if it's just HR/HE.
I wouldn't start touching the lady until she'd either started groping you, or otherwise made it clear it was ok, or as has been said, it's a mood killer.
Another mood killer is price negotiating while you're lying there with a tent pole; don't fall for it and be prepared to walk early; most of them won't let you, they'll want as much out of your wallet as they can get, although if you've been particularly mean you may get a grudging rush job which isn't worth much at all, so go carefully.
Enjoy