Hi Vic,
The {{MLA citation}} template should be appropriate for Books, Periodicals, Journals, Newspapers, and most webpage citations.
There are also 2 templates based loosely on Evidence Explained which use the same parameters as the MLA citation template. One is formatted as a "reference note", the other is formatted as a "source list" entry. {{EE source}} and {{EE citation}}. Because they use the same parameters, if you have already entered data in MLA citation format and wish to change to one of the EE formats all you should have to do is change the template it calls.
There is also a template, again loosely based on Evidence Explained, for "reference note" formatting of Census data. {{EE censusf}}
All the above are documented OR linked from: http://www.wikitree.com/wiki/Category:Source_Citations_Formatting
As you saw in the leaders discussion I had also mentioned the ability to create individual pages for sources that can be called as templates. Those pages can themselves use templates for formatting as I did with http://www.wikitree.com/wiki/Space:The_Burritt_Family_in_America and the specific template applied can be changed as a parameter when called so these 3 entries all produce different results:
{{Space:The_Burritt_Family_in_America|p=123|t=EE source}}
{{Space:The_Burritt_Family_in_America|p=124|t=EE citation}}
{{Space:The_Burritt_Family_in_America|p=125|t=MLA citation}}
While I have not created it yet, another underlying template such as {{EE citation2}} could be used to create a shorter (subsequent) citation. I had another idea related to this but have a question I need to answer before I pursue the idea.