If im new to any dungeon i watch the video to get a idea of the bosses then i announce to the group im new. Generally they are very nice and willing to work/help out.

On a side note though i have come across some..rather rude people not because i was new but thier lack of willing to work as a team. I will not name shame but some remarks were cussing, others were "we don't do this for team play" after i stated running ahead of the tank was smart in my sarcastic tone which was then met by "Idc what you think"(that was from a guildhest just today on whm) which i couldn't understand myself. People like this tend to rot the play of other people for the fear of running into their type again.

Back to topic a bad bunch can ruin a community but only because they tend to stick out more then the mass of helpful ones out there. Don't give up for every bad apple there's 10 good ones!