Are sources clearly cited in such a way the reader can locate them?
Can you verify claims presented as evidence elsewhere?
Is the content grammatically correct?
Are there spelling or typographical errors?
What to look for when determining accuracy:
For web pages, look for links to outside sources, and pay particular attention to whether the link leads you to an error page or is otherwise nonfunctioning -- this indicates the author/creator is not being careful when linking, is negligent in updating links, or, even worse, is attempting to "fake" links to outside sources.
If the author/creator links to outside sources, visit those sources:
Is the author/creator of the original source misrepresenting the linked material (which would make the original less accurate)?
Does the linked source material stand up to a critical evaluation?
The top-level domain of the URL indicates the type of organization responsible for the website, which can give you clues about accuracy. For example, in the URL library.eku.edu, the top-level domain is .edu. In general, .gov and .edu pages are more accurate than .com and .net pages.
For books, journals, or magazines, look for footnotes, endnotes, or links/references/mention to/or outside sources.
Scholarly articles and books are extensively documented with quality sources.
Popular information sources (and much information found on the open web) rarely cite sources in full; however, more reliable popular sources should provide enough information (like the original source title and/or author) to track down sources.