Because bad sources can mimic good ones, it's important to use multiple methods to evaluate your sources. Ask a librarian for help. One way is to move away from your initial source, often by Googling elements of the source. This is the SIFT method, or 4 Moves.
Investigate the source
Find other, different, or better sources
Trace back to the original source to understand the original context
Another more well-known way to evaluate your sources is to look towards a source and analyze the source itself. Librarians often call this the CRAAP Test.
Currency: Information timeliness
Relevance: Importance of information for your project needs
Authority: Who created this source and why
Accuracy: Reliable, credible, and true
Purpose: Reason for existence
Ask yourself these questions as you read a document.