Give an example of a player not using good etiquette when playing tennis

an example of a player not using good etiquette when playing tennis is failing to clearly call out the score before each serve.  Know how to call the score when you are serving. Understand how each set is scored. Know that you must always win by two if there is a tie. Know when the match has been won (or lost).

Explanation:

Etiquette refers to the set of ethical rules that you must follow to have a good behaviour in front of others. So, hitting your racket after you lose a point isn't a correct response and it shows that you don't have etiquette at all.

Another examples could be, shout at the referee on every foul or insulting other players.