See wp:Help:Editing for a comprehensive documentation about the wiki markups.
Page names all start with capitals (wiki enforced) but all the rest of the works in the phrase should be lowercase unless they are an acronym like BOSC.
To link to Wikipedia just add the prefix wp: to the word. The wp: will show up in the link name unless you specifically specify the display name. For example, to link the wikipedia entry on Bioinformatics you would use this
Everything after the | is the text that will be displayed as the link's name.