You know these guys, they're the ones who tell you how great they are, how bad you are, and how they're going to go about beating you. That's all fine and good in some situations but there are a few things you should consider before you engage in that sort of thing:

1. Know your opponent. Some people like to have a bit of fun with it and some don't. If you haven't established some sort of rapport with the person throughout the evening, err on the side of caution and just be respectful.
2. Never talk down to a weaker opponent [unless of course the weaker player is the one engaging the trash talk]. This is just bad form and bullying and no one appreciates that. You can do it to a player of equal ability or to a better player but never to a weaker player. Also keep in mind that the weaker player may soon become a stronger player and you could be in for a rough evening on the board one night.
3. Keep it light. A little bit of teasing is OK but any time you have a room full of males and beer flowing freely someone is bound to take something the wrong way.

	Rattling darts in their hand while you are throwing
	Standing behind an opponent and mumbling distractions
	Taking their time going to and walking away from the board because they've noticed that you have a fairly quick pace to your rhythm
	Purposely bending the wires on the board or slightly tilting the board while removing their darts
	Making comments after each dart that you throw
	Speaking to or about a player while they are shooting or as they are approaching the oche
	Saying things to make you feel guilty about winning or to shatter your confidence after a miss
	Announcing aloud that the game is over or putting darts away prior to your opponent actually throwing for the double
	Squeeze your throwing hand tightly during a handshake or fist-bumping your throwing hand harder than need be
	Showing up excessively late for a match or taking an inappropriate break in the middle of a game
	Displaying excessive temper during a game such as banging the wall, throwing darts in anger, mumbling your frustrations aloud, and cursing loud profanities
	Refusing to shake hands after the match
	Standing in the peripheral vision of the shooter
	Refusing to finish the match or leaving unannounced in the middle of a match
	Unnecessarily crossing in front of the shooter after retrieving darts
	Beginning your throw while the opponent is still retrieving their darts

    This is by no means an exhaustive list, but it does describe some of the most common shady behaviors. It should be noted that dart etiquette is not meant to remove the fun from darts. To the contrary, it is meant to preserve the fun in darts. Some people attribute dart etiquette spokes people as whiners or too serious. And by doing so, contribute to the growth of an unhealthy dart community. Good dart etiquette is simply just common sense and respectful behavior. There is no contradiction between fun and competition. They are words with mutually exclusive definitions.

    Darts is a sport such as golf, bowling, etc… where defense does not exist. There is no defense in darts! Only offense. To win, your offense must be better than your opponent’s. Plain and simple.

http://www.billiardroomgames.com/Rules-Darts-etiquette.html

http://www.crowsdarts.com/dadoofus/article12.html

http://www.sfda.net/clinic.html#etiquette

http://www.a1darts.com/dart_rules/etiquette.html

http://www.diamondvalleydarts.net.au/etiquette.htm

http://en.wikipedia.org/wiki/Gamesmanship