Neuro-Linguistic Programming
Links to NLP pages:

If you want a good example of influence / persuasion, then visit Marc's site. See if you can spot the influencing techniques he is using in the page.

Wondered how Derren performed one of his most remembered tricks at the dog racing track? Here is an extract from the "Spirit of NLP" typed out by a member of Yahoo! Groups Derren Brown:

"..begin by doing something shocking or unpredictable which totally interrupts the persons present state [Derren bangs on the window frame]. The purpose of doing this is simply to create a shock effect. When they receive a sudden shock they go into a confused state where their critical mind goes on hold and their perceiving mind looks for meaning, looks for a program. And of course this is your cue. Once you have provided your initial shock, quickly follow it up by giving the person an idea or a suggestion as to what is to replace the missing program [Derren says "This is the dog you are looking for"]. Give them the next step in the process instead of the one you just removed. Supplying this next step offers them something solid to grasp while they inwardly sway from the confusion."

Actual extract from the chat with Derren online:
Iamontheinternet: how much money did you win at the dog racing track in the past?
Derren: How much? Not telling