Lateral reading is an evaluation strategy that's especially helpful in the online environment. You take the name of the website (or article, or book, etc.) you have, and search it online to see more information from others. Remember that websites with biases tend to present themselves and their viewpoints in the best possible light - if you truly want to evaluate it, you will have to go outside. See more below!
As a way to help lateral reading evaluation, Mike Caulfield at Washington State University created a method he calls the Four Moves, or later called SIFT. SIFT stands for Stop; Investigate the source; Find better coverage; and Trace claims, quotes, and media back to the original context. This method, as with lateral reading in general, puts an individual source back into context. It allows you to evaluate it in the larger information ecosystem, rather than as a silo all its own.
Note - in finding "better" coverage, this refers to coverage that better suits your needs. To avoid confusion about one source being objectively better than another, I have changed this slightly to "Find Other Coverage".
STOP: Look over what you have using the CRAAP test or other vertical evaluation. Remember what your purpose is. What do you need from this source, and what type of information do you need it to provide? What are the major claims being made here? Do you see any issues that should be verified or investigated further? Make a plan to put this source in the context of other information, not just what it presents here.
FIND Other Coverage: In searching for information about the source you found, did you find other sources on the same question or topic? Are those sources in consensus with the source you originally found, or do they have different information? Would these new sources be more appropriate for your information needs? Apply lateral reading to the new source - what are other websites or organizations saying about this new source? How does this new coverage put your original source in context?
INVESTIGATE the Source: What can you find online? What do other organizations say about this source? Does this scholarly article have any associated commentary, editorials, or corrections/errata? Has it been retracted? Where does your news source or website fall on the political spectrum? Has it been investigated by fact checkers? Who funds the source?
TRACE Claims, Quotes, and Media Back to the Original Context: Trace the content back to their original context. If a blog post refers to a scholarly study, find the original study - does it claim what the website claims it does? Has that study been retracted or otherwise edited in the meantime? Research the claims made on your source. Does the general scholarly consensus agree with what is stated? What is the original context for these claims?