This achievement is pretty easy to get if you're starting up a new save. When going through the game, multiple characters will ask you for help with a task and you will be presented with an option to say "yes" or "no." You're going to want to click no for this achievement to pop. (Don't worry, you can talk to them again and hit yes after.)
However, if you're like me and have already beaten all the levels and still have this achievement to get, you're going to want to load up the level "Outback Safari." Once loaded in, head over to the bottom left of the map and talk to Ranger Ken who will ask you for help putting out the fires. (He will ask even if you've already done it) Simply click no and the achievement is yours.