The MediaWiki software we use for Wikivoyage has features for making links between articles that cover the same topic in different languages. These are called inter-language links.
To add an inter-language link to a page, put in a link at the bottom of the page in the following format:
- [[language code:article title]]
Here, language code is the two-letter code for the language of the Wikivoyage language version you're linking to; see the Wikivoyage home page for the list of Wikivoyage language versions and corresponding codes. The article title is the title of the matching article on the other language version.
The inter-language link will not show up in the article text. Instead, it will be put in a special "Other sites/languages" section of the page. This kind of link is for articles on the exact same subject on the other Wikivoyage language version.
Each Inter-language link should go right at the bottom of the page on a separate line. The inter-language links should be ordered alphabetically according to their two-letter codes. It's hard enough for new Wikivoyagers to figure out how to edit a page; we don't want to scare them off with a whole bunch of formatting stuff and foreign words right at the beginning of an article.
Different subject 
You can link to a page on a different subject using this syntax:
- [[:language code:article title]]
Note the colon (":") at the beginning of the link. This makes the link appear in-line in the article text.
Inline links to other Wikivoyage language versions are rarely helpful to travelers, and should be avoided for destination guides and other articles in the main namespace. However, they can be useful for talk pages or other places we discuss how to make the guide.