Where deliberate deception is not an issue, there is still room for errors to seep into the material due to unchecked facts, inadequate or outdated science, deception on the part of others who informed the writer or speaker, commercialization of the academic community, and many other reasons. In general and normal reading, there should be a great deal you disagree with, if you are of a skeptical bent. Much of the material you will come across is not true or only half truth. Ask yourself if what you are reading is trustworthy and if you agree or disagree with the author as they make each and every claim. One skill you must develop is the ability to distinguish facts from claims.
Facts are statements that can be readily checked, as in an encyclopedia or other reference work.
If you read that Betsy Ross designed the American Flag, for example, it should not be hard to either verify or refute this statement in many reference works. Question facts when the writer may have something to gain from their use. If Scientology, for example, states that they have 8,000,000 members and uses this fact to gain credibility and recognition, it may well be a claim that needs looking into and independent verification from another source, such as a census or checked against other numbers from the organization such as numbers of churches and members at each. An opinion or a claim is a statement open to interpretation and judgment. Claims are not necessarily open to the kind of checking that facts are.