Psyching the opponent out is by no means a new concept. This is especially noticeable in the international arena where a small number of the same fighters come to know each other over a period of years. Former British world-class karateka Vic Charles MBE often fought the French fighter Pyree and when this happened, Vic's confident and aggressive demeanour always suddenly changed for the worse. Talk to your opponent before the bout. If he seems nervous, then it may be a good idea to tell him how successful you've been in the last few bouts, pointing out that several times you narrowly missed being disqualified for hospitalising someone.
Some fighters like to prepare for a fight by stalking around on their own.
They become antisocial and avoid others, so if your opponent is one of those, then go over and talk to him. Don't be put off if he seems to ignore you, just keep talking at him and with a little bit of luck, you might succeed in totally disrupting his mental preparation. Other fighters don't like watching how the other bouts are going so tell them what's happening. If this sort of thing appeals to your twisted mind, then buy a copy of John Cleese's video How To Irritate People . Not only is it a good laugh but it shows just how many ways there are to ruin someone's concentration.