Authority- Who wrote it? Who said it? Are they expert in this field? According to whom? Authority can be tricky to determine; someone may be an expert in one field but holding forth in another. Even in academic circles there may be cranks.
Content, Currency--What content is available? Is it in a form you can use? How recent is it? Currency matters more in some fields than others; nanotechnology changes fast, where English literature develops relatively more slowly.
Relevance-- does the material apply to your topic? Does it make sense in relation to what you already know? Relevance is hard to judge until you've read the material, but for an article, the title, the abstract, and where it's published (the journal title) may give clues.
Effectiveness and efficiency--Is this material appropriate to answer your question or support your idea? Is this material available? Is something else as good available more readily? Efficiency is partly in knowing what to look for, knowing who to ask for help (your librarians) and then if possible using what is here, first, then using interlibrary loan if needed.
Substance (and stability)--Is the material adequate to support your project?Is it of a kind that is considered reputable? Substance is defined by the utility, quality and sufficiency of the materials. If you can use it, it is of good (or better) quality, and it is enough to support what you are doing, then it is of the right substance. Stability, in Web resources, is a question of whether the source will be available over time.
ACRES is an acronym I developed for evaluation of Web resources, but it is useful for most types of materials. Since this is a land grant university, I thought it was apt.
Parker-Gibson, Necia. "ACRES: Accessibility, Content, Relevance, Effectiveness and Stability of Internet Sites."(1997). In Unmasking the Internet for Research, Using Hands-on Active Learning Exercises, ed. Marilyn P. Whitmore, 123-133. Pittsburgh, PA: Library Instruction Publications.
What is considered a primary source varies somewhat by discipline. In any case, think of a primary source as first-hand knowledge, eyewitness accounts or testimony about _(whatever topic)_.
For history, a primary source is a letter, a diary, speech, lecture, piece of legislation, document or manuscript-- in other words, an original source which then forms the basis, along with other sources, of other, secondary work, such as a study of life in eighteenth century Ireland.
A narrative is "[A]n account or narration; a history, tale, story, recital (of facts, etc.)," according to the Oxford English Dictionary. In other words, a narrative is usually a personal account, by a single individual, of a period of time or an event.
In the arts, a primary source may be a piece of art, such as a painting or sculpture, a musical score, a poem, a book or chapter, or an essay--whatever is created by the artist, writer, photographer, etc.
In the sciences, a primary source is the first report of research; it may be published as a journal article, or sometimes as a research report or conference proceeding.
In some of the social sciences, such as anthropology, ethnography, psychology, sociology or social work, a primary source may be the first report of a piece of research, as in the physical sciences, or it may be something closer to primary sources in history, since some areas of these fields depend on direct observation, data, personal narratives or commentary, as from interviews or case studies.
A secondary source is based on a primary source or other sources. It includes analysis, criticism, or other intellectual input. Secondary sources include books, book chapters, articles, especially literature reviews, and some book reviews. Some bibliographies, if well annotated, are considered secondary sources.
A tertiary source is commonly a resource or tool that helps people find primary or secondary sources. Tertiary sources include most bibliographies, databases and indexes, and library catalogs.
What's gray literature? Gray literature is information that is usually not published for the general population, but available in limited distribution, typically to persons inside a company, a discipline, an industry, or a government sector. Examples include white papers, preliminary reports, brochures, handouts, working papers, notes, and so on. Some gray literature, such as in as scientific or engineering areas, is fairly well indexed and easy to find.