Eprints tags are used in the EPrints academic repository software. BE Press tags are used in The Berkley Electronic Press SelectedWorks product. Neither offers documentation on their proprietary meta tags that I could find.
You can, however, view the source of any HTML page generated by an Eprints or SelectedWorks server to see their metadata tags in use. For example, viewing the source on this page from the University of Southampton's Eprints server shows Eprints tags in use, and viewing the source of this page shows BE Press tags in use.
PRISM tags and use cases are provided here. The PRISM Cookbook 3 [PDF] gives an alphabetical listing of all PRISM tags at the back, though there's no specific reference to preparing tags for Google Scholar.
Honestly, though, unless you're using EPrints or SelectedWorks to publish research, or you're part of a publishing house that already uses PRISM in their workflow, I would simply use Google's suggested
citation_ tags as referenced in the inclusion guidelines you linked to. From their example:
<meta name="citation_title" content="The testis isoform of the phosphorylase kinase catalytic subunit (PhK-T) plays a critical role in regulation of glycogen mobilization in developing lung">
<meta name="citation_author" content="Liu, Li">
<meta name="citation_author" content="Rannels, Stephen R.">
<meta name="citation_author" content="Falconieri, Mary">
<meta name="citation_author" content="Phillips, Karen S.">
<meta name="citation_author" content="Wolpert, Ellen B.">
<meta name="citation_author" content="Weaver, Timothy E.">
<meta name="citation_date" content="1996/05/17">
<meta name="citation_journal_title" content="Journal of Biological Chemistry">
<meta name="citation_volume" content="271">
<meta name="citation_issue" content="20">
<meta name="citation_firstpage" content="11761">
<meta name="citation_pdf_url" content="http://www.example.com/content/271/20/11761.full.pdf">
Of these, Google says they only need the
citation_author, and the
citation_date in order to index your work, but I'd suggest providing as much information as you can based on the supported tags they list.