To access these hidden settings you simply need to type commands (listed below, right in 'Get hidden settings') one at a time into your chat box and hit [Enter] - the moment you hit a '/' you'll start typing them in. Some people have found that reloading the UI (type / 'console reloadui') makes things prettier, although we haven't noticed this ourselves. Either way, it gives you control over rendering values that isn't possible using the slider systems alone.
You can enter these settings manually just to see what difference they make, but it's probably wiser to create a couple of macros that can change the settings on the fly. There are times when you'll need performance (in a raid, for example), and others when you just need the game to look as good as humanly possible (soloing). Once you have the settings as macros you can tailor them easily to suit your own needs, and just hit the buttons when needed. Beautiful.
How to make WoW gorgeous
You have plenty of control over WoW using the default video settings, which can be accessed from the main menu, but the limits of these sliders are lower than what the game is actually capable of (1). For instance, the Ground Clutter Density slider has an in-game maximum setting of 160, but the corresponding console command lets you push this all the way up to 256. The difference is pretty breathtaking too - with not only more vegetation, but higher and more lush plants at that (2). It also makes more stones, but that doesn't excite us quite so much.
We've actually set up two macros to enable us to stand anywhere and see how the rendering engine handles the highest and lowest details. In order to create a macro, simply hit the Macro button from the main menu (hit [Esc] a few times until it pops up). Give your macro a name and a suitable icon and then type in the commands below. Repeat the process for the second macro, then drag both to a free spot on your action bar (3). Stand in Terokkar Forest or Nagrand and hit one and then the other and grin like a loon.
Once you use these settings, there are times when you'll be particularly aware of the draw distance of the local objects. Unfortunately groundEffectDist is limited to 140, so there's nothing you can do to improve this value (4).
Get hidden settings
Create a macro inputted with the following to see WoW in a new light:
/console groundEffectDensity 256
/console groundEffectDist 140
/console detailDoodadAlpha 100
/console horizonfarclip 2112
/console farclip 777
/console characterAmbient 0
/console smallcull 0
/console skycloudlod 3
If your framerate takes a dive, then this macro will sort you out:
/console groundEffectDensity 16
/console groundEffectDist 1
/console horizonfarclip 1305
/console farclip 177
/console characterAmbient 1
/console smallcull 1
/console skycloudlod 1
/console detailDoodadAlpha 1