It is nicely demonstrated in the Table of Contents of the Markdown Cheatsheet. ##### Table of Contents [Headers](#headers) [Emphasis](#emphasis) …snip… <a name=”headers”/> ## Headers If you hover over a Header in a GitHub Markdown file, you’ll see a little link sample to the left of it, you can also use that link. The format for … Read more
Append .wiki.git to the repository name. That is, if your repository name was foobar: git clone git@github.com:myusername/foobar.git would be the path to clone your repository and git clone git@github.com:myusername/foobar.wiki.git would be the path to clone its wiki. Note: You must have at least one page to be able to clone the wiki repo. (via @tobiasz-cudnik)
GitHub doesn’t support pull requests for the wiki repository, only the main repository (this is a bit of a shame, IMO, but I can understand it). Here’s an interesting way one project manages community updates to their wiki, while still keeping tight control, as for source code: My proposed workflow is this: Manually create a … Read more
Some color-syntaxing enrichment can be applied with the following blockcode syntax “`json Here goes your json object definition “` Note: This won’t prettify the json representation. To do so, one can previously rely on an external service such as jsbeautifier.org and paste the prettified result in the wiki.
Updated: Markdown syntax for images (external/internal):  HTML code for sizing images (internal/external): <img src=”https://github.com/favicon.ico” width=”48″> Example: Old Answer: This should work: [[ http://url.to/image.png | height = 100px ]] Source: https://guides.github.com/features/mastering-markdown/