Beyond the obvious, this is a very, very open-ended question. While VLC does have a focus (as a media player), the library it's based on is very complex, and lets you tweak just about anything. Wanna tint the video neon green? You can do that. Would you want to? Probably not. Most of the tweaks that you can do are very specific or already at the best defaults for the general populace (you might want to set a tint if your TV/screen is tinted itself, i.e., correcting colors, but that's not something you'd find in a guide).
If you're wanting to know what the various settings do, either fiddle with them and see what they change, or google the term to find out more information about it.
The only tweak guide that I've found worth mentioning is enabling proper upscaling on VLC. It used to be enabled by default on older versions, and then for whatever reasons it stopped being set in the defaults. I don't know if they've shipped it as default in recent builds, but here's how to enable high-quality upscaling.
Beyond that, if you want to know how to do a specific thing, feel free to ask, and you'll probably get better answers if we know what you're looking for. VLC is an open-source application - anything that could be put in a tweakguide.com-style guide has probably been already added to the code as a default.