Big Trouble in a Talking Barrel?

As you can see here you have to stay near the barrel until he says all the 6 lines of text,the achievement will be completed as soon as he finishes his 6th line.

In case you break the barrel before achievement is finished,you can always come back by re doing the quest.

NOTE: That not every chat line is counted as complete line and some are repeated so check your achievement progress before breaking the barrel.

List of thing he can say(it is randomly chosen):

• "Hello? Is anyone out there?"
• "Am I talking to myself? Don't answer that."
• "If you could just smash this barrel open, I would be much obliged."
• "What's going on out there?"
• "Are you dead? If you're dead, just say so."
• "Are you still alive out there? Or is it the monsters?"
• "Say yes if you are. Or you could clap."
• "Hello! Is there anyone alive out there?"
• "I'm not actually a talking barrel. Don't worry about breaking it. Me."
• "This wouldn't be quite so bad if I could turn around. Wait a minute. I can turn around."
• "It's terribly messy in here. What is this... blood? Who stores blood in a barrel? Oh, it's wine."
• "Maybe I could tip the barrel over and roll around. It could work. Or give me a headache."
• "Just a little whack should take care of it. Not too hard!"

A list of everything he says can be found here: http://diablo.wikia.com/wiki/Big_Trouble_in_Talking_Barrel

According to a comment at http://d3db.com/achievement/i/big-trouble-in-talking-barrel you apparently do get the achievement before breaking the barrel, so stand near it and be patient. I don't have the achievement myself, so I can't confirm, but as it's about a half hour after posted I'm guessing you've answered this for yourself anyway. :)

Just completed it, 5/6 for a while but after breaking Every other vase/barrel in the room he said the last line and I earned the achievement. Hope that helps.