You can remember how to do this with the acronym TCP OK; T is for tone, where you discuss the expression in the source- is it biased towards a certain side, or trying to persuade? C stands for content, where you can fact check your own knowledge of the subject (the OK) against the actual content of the source. And P stans for provenance, which is where the source is from and who it's by, and the form it takes. If you discuss all 4 of these things, you'll have a well developed paragraph.