Another question every new mapper asks himself is: What makes my map/setting "real"? A lot of new mappers start off with a location or setting that doesn't need a lot of creativity and so did I. I though about creating a UAC Base with some resting rooms for marines, with a bed, a computer, a toilet and all that stuff that - out of a logical thought - must be found in a certain area of this UAC base, but honestly: "Little Did I Know!" Shot 1 shows a very old map of mine (my second map overall) and to be honest, it looks like total crap and has nothing to do with a "Real Place!" Two important rules: 1st, never ever create sector based objects from your real world (beds, wardrobes, and so on), use sprites and 2nd, if you still want to create that, never use original Doom textures for that (create new ones). You see, this is somehow a bit complicated: Although it makes sense to have toilets, beds and wardrobes in a UAC Base, it totally destroys the map!

Now you may still ask yourself: "Eh? So what is it all about with this Realness in my map?" The answer may surprise you but it is indeed quite simple: This doesn't depend on the amount of real objects in your map or on the architectural logic concerning routes to go or how the statics work, it only depends on the arranged atmosphere and beyond on the overall theme of the map. You don't believe me? Well, just check "The Ultimate Dooms" maps and ask yourself: Does any of these rooms or halls make any sense? The majority does not, so stop searching for rooms. Still, Episode 1 of Doom is one of the most popular mapset. Or think about Torment & Torture 2. A lot of people told me, that they loved the map because it felt so damn "real" but if you take a closer look on the whole installation (rooms & roots)...in some places, it absolutely has no sense :) It felt so real because I made the atmosphere and setting go hand in hand, it made sense how things turned out in the end.
The contra example (shot 3) is "Batman Doom". It actually presents a lot of beds, wardrobes, computers and other things in its maps,but (!) it doesn't interfer with the 2 important rules, because it uses new resources and new material and beyond - being a TC - has a certain overall theme that allows the usage of these things.
So you see: It doesn't matter if you are about to create a super realistic city with all the bureau rooms, toilets and cars or if you create something out of your mind that doesn't actually exist. Both things can feel perfectly real, it just depends on the execution.

Summary: "Reality Depends On The Arranged Atmosphere And The Overall Theme, Not On The Amount Of Real Things In The Map"