Had this problem yesterday. I liked how they worked NPC dialog in oldschool EverQuest. Everything your suposed to talk about is listed in brackets like this [].
-Funny Example-
Guard, Says "Hail citizen. Welcome to freeport. Stay away from [boomba]."
You, Say "boomba"
Guard, Says "Aye. That large [ogre] over there who's sellin pickles. If you get to close you might be the next thing he pickles."
You, Say "ogre"
Guard, Says "Now don't be makin me explainin ya what an ogre be... Go frolic with a [gnoll]."
You, say "gnoll"
Guard looks around paranoid and lost for words.