Almost every publication, journal or conference series seems to have its own style guide. Is anyone keeping track of these ? IE, is there a website which keeps a list of style guides - specifically citation styles - for various publications ? The most definitive (ie all-encompassing) list would be what I'm after.
This Wikipedia may be a good starting point.
There are the international ISO series. And just in the US there are style guides for general writing, legal documents, academic papers, journalism, electronic publishing, business, and computer industry. It may be better to limit your scope of study.
A dedicated literature reference software may help you to keep track of the publications already accessed, as well in cross-linking them together (for example with a mind map; like docear), as well as easing insertion of the citations in your word processor / editing software. Beside an article about it, wikipedia holds a list to compare them.
After collection of your readings, you will benefit from their style library, simply select "this publication is for Nature", and the citations will be formatted accordingly. If you you want to use the citations again, for a different journal, reformatting is just a click away.
Personally, as working in an environment of different operating systems, I prefer zotero with a large -- and extensible -- library of styles, and "connectors" to Microsoft Word, LibreOffice Write, Apple's office, and LaTeX.
In addition, university / research libraries often offer workshops how to work with such tools. Because of personal preferences, I recommend exploring them, side-by-side for some time prior to make a decission in favour for one or/and the other.
Many reference managers can format citation styles automatically. This is a case where LaTeX is probably not your friend. A search of CTAN reveals around 43 styles for Biblatex and my TeX Live 2016 install has 404 bst files for Bibtex. In contrast, Endnote offers more than 6000 styles and Zotero has 8341 styles. I believe Mendeley uses data from CitationStyles.org which claims to have over 8000 styles.