Paragraphing
There is a degree of flexibility when it comes to the matter of where and how often to start new paragraphs. Sometimes a subtle point in an argument will require a paragraph of almost an entire page to elaborate; occasionally a single sentence can form an effective paragraph. Yet separating ideas into paragraphs remains an important aid to the processes of both reading and writing. Here are some guidelines as to when it is appropriate to begin a new paragraph:
Whenever you switch from describing one place, person, or thing to describing another.
When a new topic is introduced.
Example:
There can be little doubt that Austen's asides on the literary conventions of her time provide an amusing counterpoint to her story. But does this running commentary detract from the primary imaginative experience of Northanger Abbey?
When there is a change in direction of the argument.
Example.
To this point we have been looking only at the advantages of a guaranteed annual income. We should also ask, however, whether or not it would be practical to implement.
Description, narration, and argument are commonly blended together in writing, and it is usually also advisable to start a new paragraph when changing from one mode to another. If, for example, a text moves from describing an experiment to analysing its significance, it's a good time to start a new paragraph. If it moves from telling where Napoleon went and what he did to discussing why events unravelled in this way, the same holds true.