So, I think a demonstration in form of screenshots from a room in his different building states will be the best thing, I can supply you for the end of this chapter, here we go: One room in 7 simple steps ;)

Ok, let's start: In step one we just create the basic shape of our room, give it some nice walltexture (STARTAN in this case) and two fitting ceiling and floor flats to round up the thing, not that hard at all.

Step 2 shows one of our first tricks we learned above to gain some detail, the borders (textured with BROWN1 and STEP5). The upper border was lowered 64 units, the bottom border was raised 8 units to make it look like a small step. Also I raised one part of the room for 128 units to show off some nice height differences.

Next step - number three - I added one new ceiling window to the center of the room, also with a border, and another ceiling window in the backpart of the room further away. After this, I adjusted the lightlevels of these sectors because I already have my lightsources fixed at the top ;) Finally, I added an elevator to the backpart!

The next step, number four, looks most complex but to be honest, it is the one that makes fun and it is therefor really easy to do: "The Terminals!" :) I added several recesses, added computers, added panels and added one door. I also added some metal bars to the front top window (which you unfortunately can't see, just the shadows) and some metal bars to the ceiling-window in the background.

Step 5 adds some smaller detail which isn't visible first at all comparing shot 4 and shot 5. I added SUPPORT2 parts to every corner of the main-room walls, this spices up the plain corners a bit.

In step 6 I finally added light-sources to the ceiling and some platforms to the ground to make the floors/ceilings look more interesting diversified.

And last but not least, in step 7 I added the things to my scenery, barrels, lamps, monsters and some gore. This room has been done in 25 minutes and it really looks beautiful, doesn't it? :)

Summary: Well, with this small demo ou see how fast you can create a completely new over-detailed room within just a few minutes if you learned all the simple tricks above, that's all about it and I hope it helps :)
Extra-Buildtime: "20-30 minutes" 
Build-Difficulty: "Low - High"