Help:Editing
General instructions: http://meta.wikimedia.org/wiki/Help:Editing
Adding a user: Special:Userlogin.
Existing templates: http://en.wikipedia.org/wiki/Category:Wikipedia_templates
Citing: http://en.wikipedia.org/wiki/Category:Citation_templates
Location maps: http://en.wikipedia.org/wiki/Template:Location_map
Other
Everything LaTeX can do (can be installed, if needed): http://wikisophia.org/wiki/Wikitex