How can I quickly get to grips with a historical source in an exam?

When time is sparse, the best way to distinguish what the source is telling us to read it once and pick out three seperate lines from it.

After doing this, look at each one and describe what each line is literally demonstrating. This means you have three seperate things to say about the source with direct single word analysis. From this starting point, it is then much easier to state your argument.