Source questions are much easier when they are broken down into what we are truly asking about the source:
Is this source reliable?
Is this source useful?
It is important to note that all sources have utility, even if they are not reliable. For example, a newspaper article that is Nazi propaganda is not reliable in exposing the true motives of the Nazi party, but is useful because we can see exactly how they wish to be perceived by the German population in a public and circulated document. As well as analysing the actual content, it's useful to use the DAMMIT framework to analyse the source:
D ate - how significant is the date? Is it a primary or secondary source? How does this effect utility? Did it happen before, on the day of, or after a certain event, and would this affect the utility of the source? (e.g sources written before a large event are limited as they offer no insight into said event)
A uthor - was the author present at the time? Is the author known, and if so, what is their relationship to historical events unfolding? How does this effect what they write about (see Motive and Mode)?
M otive - there is always spin on sources, depending on the author and what they wish the world to know. Are they spreading propaganda? Or perhaps writing a confession in a private notebook, which they wish to keep? Is it a speech intended to rouse the masses? These are intertwined with the Author and Mode.
M ode - this is very important as it determines the reliability and utility massively. A newspaper article is public, so may have motivations to persuade the public or to spread propaganda. Journals or memoirs are private so may be more reliable in the truth, but are also limited in perspective. Speeches have a specific motive, and are different from other modes as they are often related to a particular event.
I ntended Audience - tied to above, who is this meant for? How is it supposed to make them feel? Is it meant to persuade or dissuade them?
T one - Angry, demanding, passive, pleading - tone is very important as it allows us to see the intentions of the author. The tone can be ascertained by language and punctuation used, and is extremely important in determining the intentions of the source.