Originally Posted by Cubituss
"Fire in the Hole" achievement is easies at the very beginning of Droid Factory level in Episode II. If you don't attack, the guards won't shoot you. So run down the corridor up to the door until all have left their caves, they will be crowding around you, still without shooting. Throw a bomb with a bounty hunter - achievement unlocked.
I got "Fire in the Hole" in Ep. IV Chapter 5 when you chase the stormtrooper down the hallway of closing doors and open the last one and there's a whole mob of them. Probably more difficult than what you're describing though.