Historians work with material that is often incomplete, contradictory, messy, and full of ambiguity. They also have to deal with people who had their own point of view and biases. For example two different witnesses to the sinking of the USS Maine might have very different explanations for what happened. One might be an expert in warfare and a ship’s captain while the other might have strong personal opinions about the cause of the sinking.
One of the things that historians do is to look at the evidence and see what it tells them about the events and actions that took place. In this way they try to get as close to the reality of the historical situation as possible. They are a bit like paleontologists who publish sketches of their skeleton finds and use dotted lines to indicate what they think the missing parts might have looked like.
This is an important aspect of how historians approach their work and that can be used as a framework for helping students understand how they can research history. It is a good idea to begin a lesson with students reading what other historians have written on the subject they are investigating, and then getting them to write their own interpretation based on that knowledge. Then they should start investigating what happened, why it happened when it did, and how the event changed other factors in the future. It is a bit like solving a mystery, investigators collect clues, make observations and inferences and then follow the trail of information that leads to the truth.