Well, over the past day or so I've been considering tricks and traps in terms of dungeon design. My thinking is that a dungeon should be built according to a coherent plan by someone. On the LRPGSW site we have a couple of posts on Dungeon Design. The first was a series of Purposes for dungeons along with brief descriptions of what their natures are and what they generally are like. An example is "A Sapper's Tunnel". While not normally considered a Dungeon per se, it still fit into our general idea of "Places underground that can hold adventures". The description reveals it to be something like a short tunnel that goes under a castle wall. It may have corpses (who could be the basis for ghosts or undead perhaps) and perhaps tidbits of treasure and probably armor and weapons. It is probably hastily constructed, dangers, with no irrigation for water (fetid pools), and be populated by insects, rats, serpents, etc. Maybe a kobold lair. Etc. That's one example.
I then went on to discuss in a later (most recent) post some thoughts on tricks and traps in terms of dungeon designs. Now I'm considering fusing the two together to get a comprehensive Dungeon Builder's Guide of some sort. It's been interesting to contemplate. In support of the goal I am reading about ancient and medieval war, along with a very good book on ancient techniques of biological and chemical warfare titled, "Greek Fire, Poison Arrows & Fire Bombs" by Adrienne Mayor. An excellent read and a great resource for this sort of thing.