[thewisedude]

Information is Power==Money!

One thing I always believe helps is having information about the thing that you want to buy. For eg:- If you know that the car that they are trying to sell has been sitting in the lot for more than 2 months, then you know they are desperate to get rid of it, so you can come up an appropriate(much lower) ask price!

In all fairness, adding in the nibbles may annoy or piss of the person you are dealing with(in some cases). In a way, you are sort of pushing them into a corner.

However, expanding the pie and looking out of your tunnel vision is a useful hint!

Also, in the case of FBI negotiator, not everybody will let you sleep over their offer when they have matched your ask price without you giving them any wiggle-room.