Sharking
Don't shark. Sharking is "cheating". If you win a match by sharking your opponent, then you did not really win your match. You know you won the match by cheating. You know you did not "really" win. Other players know this as well. It is nothing to be proud of. Following are some common sharks, avoid them!
Anger (Making your opponent angry)
*Wrongly accusing your opponent of cheating; accusations of improper lag, improper coin-flip, improper shot, etc.
*Accusing your opponent of something they did not do or did not intend to do.
Concentration (Disrupting your opponent's concentration)
*Doing anything vocal or making noise while your opponent shoots, is approaching the table to shoot, is studying the table for next shot, or is racking balls for next game. This includes talking to other people during the match.
*Any comments or questions about your opponents playing/shooting good or bad.
*Coaching your opponent. Don't coach other players unless they ask for advice. Unsolicited coaching is a shark.
*Criticizing your opponents game.
Distraction (If what you are doing would distract you while shooting, it probably distracts other players)
*Moving deliberately within the shooter's field of view.
*Standing where opponent needs to be for next shot.
*Waving your hand while your opponent is shooting or about to shoot.
*Standing at the table, especially behind the target pocket.
*Chalking your cue at table when it is your opponents turn to shoot.
Psychological Tactics (Upsetting your opponent or disrupting their confidence)
*Using psychological "tactics" before the match/tournament begins - Negative implications/comments/questions to players you may play in future games.
*Statements, implications, or questions about your opponents missed shots in prior games - Trying to make your opponent think about their poor shooting.
*Statements, implications, or questions about your opponent's losses in prior games - Trying to make your opponent think about the previous game they lost.
If you are doing any of the above, then you may want to work on being a better sport, just like you work on playing a better game. If your opponent makes an unusually good shot, "tap" the butt of your cue on the floor three times. You will find that good sportsmanship and good playing ability go hand-in-hand. Treat other players like you would like to be treated by them. Pool is a competition, the other players want the same opportunity you do to plan and execute shots without interruptions.
If you lose a game and this upsets you, keep in mind that even the best players have their off days and lose games. Sometimes the "roll of the balls" at the break will determine the winner. Even the best player is left helpless with certain situations. (This is where "luck" comes into play. Try a rabbits foot!)
Only one person can win first place in a tournament. Be a good sport and shake hands with your opponent after each match - win or lose. If you don't win the tournament, remember the shots you need to work on and practice them daily. Most importantly, have fun!