How do I assess the usefulness of a source?

The two most important things to consider when analysing a source are provenance and content. Provenance means where the source comes from, so ask questions like, who created the source? Why did they create it? If it's an account of a historical event, did they witness the even first-hand, or are they relaying what they've heard from other people? Are they (or are they working for) someone with a vested interest in how the subject of the source (the event, person, activity, or thing that it describes) is presented? If so, the source is likely to be biased, but this does not necessarily make it less useful! For example, a manifesto for a political party will obviously present the party and its policies in a better light than its opponents, but it can still be useful for learning how the party tried to appeal to voters and why people did (or didn't) vote for them.Content means what the source actually says. An important skill here is cross-referencing, both with other sources and with your own knowledge. Does the source say something which you know is false? If so, we might be reluctant to trust other claims that it makes. You should also consider how relevant the source is to the question being asked. For example, a medieval poem celebrating a past military victory may be useful for learning about how people at the time viewed their collective past and the deeds of their ancestors; however, it may not be a very accurate description of the actual events of the battle.