Actually I'm currently working on that now. I've got a guide going with some screenshots and a Glossary of terms for better understanding. It's just been started, but it might help a bit. It's focused for advanced tweaking with a custom enbeffects.fx file, but it won't be long before the basics are up with screens too. It's the second link in my sig.
Edit: Another tip I can offer is if you're using ENB . 132 or above, open the GUI in game, disable everything, and enable one thing at a time tweaking one value at a time, based on your location, outdoors or in, and time, day or night and see what it effects. Rule of thumb, if you don't notice a difference, set it back to default and leave it alone. For instance, Point Lighting won't be effected unless there is an alternate light source such as a campfire or torch, same with Light Sprite. You'd be surprised to find what is and isn't. Such as the fog in a swamp isn't controlled by volumetric fog, but rather Particle settings.
If you try this and you want to revert back to the one you're currently working on, make sure you back it up for use later.
Edited by ChaotiKPranXter - 4/28/13 at 4:16pm