Well there are a great many different things you can list about this subject. Personally a few things that come to mind..
I also do the stare thing.. but chances are... the times your trying to stare down your opponent your in such a mood that your probably losing the match because your playing badly, and you want to turn the game around off of the table, because you arent doing so on the table. But if you so happen to be seated 180' your opponent, directly in front of their vision, then it doesnt hurt to give them a glare.
Also, something subtle ive been doing lately.. i always chalk my cue after i miss a shot, kind of like a reflection second, where i can analyze why im having to sit down. So as im walking to my chair, if its on the way, i will place the chalk in their field of vision, preferably right next to the pocket their aiming at. Dont know whether it works or not, just something i started doing.
Also, i knew a good A player who really was affected by "chalk down" people. He HATED it when people would do that, place the chalk facing down on the table. He often talked about playing people in tournaments and whatnot who did this, and talked about how mad it made him. So this is another subtle tactic you can use.
Also, if your already winning, and you start noticing someone is on tilt.. you can slow down your game a bit, this will do the finishing touch, especially in a money game, where if your down, time is key, like my friend says "time is money". If you take an extra 5 seconds or so on the shot, lining things up with your cue, or checking meticulous things, like the 3rd/4th ball in your runout, it can severly shark your opponent. normally when people are down in a match, they make the mistake of trying to play "faster" for some reason, trying to make up for their losing position. If you take extra time, this will interrupt that, and it makes them really angry.
Also i know some people, myself included, hate REALLY slow players. So if your in a sticky situation, and want to do this, i guess go ahead, but chances are if you took 5 minutes/shot when playing me, it would be our last set

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Theres also so many verbal ways to shark your opponent, but these are so obvious and dirty, i wouldnt recommend using your vocabulary to win a pool game. Trying to shark an opponent with words is particularly annoying.
One thing to kinda throw someone off is to get the rack for them after u win a game, as to remind them that they lost and its their time to rack. I think this one is pretty funny.
Also if you want to SURELY shark your opponent buy them a
betmore-ready-rack