I have written an entire walkthrough for this achievement over at xbox360achievements.org. For convenience, I will simply provide a link to the forum post, as the guide is very long and has formatting.
VISIT MY "GUNLESS WONDER" WALKTHROUGH HERE
http://www.xbox360achievements.org/forum/showthread.php?t=24...The walkthrough contains very vivid instructions and guidelines on what to do. I would have reposted it here, but I figured it would just be better to provide the link to the original post.