The times we are in are bleak for a lot of people stolen or tricked into prostitution or slave labour. There is a huge thing on cnn at the moment about that sort of thing.
The best way to find human trafickers is to lay possum for them. If the police were to go undercover they could find out a lot.
How much is this worth for prostitutes? If you were to make them your escort and asked them to take you for a good time, they would no doubt try to get you to buy them drugs from thier dealers. THis would open a whole can of worms, so soliciting could take place and go a lot faster than going undercover.
The best way to get to slave labourers would be to try to get something built in India or wherever for as cheap as possible. Once they have them on the books they could try to ask for identity documents of their employees or something. This will bring them into close contact with the slaves and then they could send the labour slave drivers away for a while, to a meeting, and make a plan with the people that are slaves for thier well being. In fact the West could buy off thier contracts, all of them, for under a million dollars, as rupees are nearly nothing in to day's climate and giving the rupees to the slaves would ensure them being able to say they have paid off thier debts and may go. I am under the impression that the typical rupee debt is about two thousand rupees, so converted into dollars means that they could buy them off for next to nothing! They could even start a charity for this, a basic small charity, or, if the state is interested, they themselves could buy the people out with a pittance of thier circulating cash.
But in both cases there remains the problem - what will they do then?
In some cases they may be glad to remain in thier respective slavery. In this case due to drug addiction or lifestyle of food funneled into the system this could damage a system where people are evidently fed too. In this case there needs to be jobs for them to come out towards. With the skills they learned in the slavery types they were in, they could build for a company or go undercover to route out drug dealers.