Here is an example of how not to organize your paragraphs:
As an adult living at Thornfield, Jane learns the secret of a hidden room containing the insane Bertha Rochester. There are no windows, rendering it dark and loathsome. The figure of Bertha stands out in the gloom as an unrecognizable beast that "grovel[s] and growl[s] like some strange wild animal" (220). This image compares to that of the unrecognizable mirror image in the red room. Jane takes in the episode of the hidden room and waits until she returns to her own room to think about it. Even though Jane is in love with Rochester, she refuses to compromise her morals and become his mistress. However, just as she is leaving she stops at his door, but moves on. Thus she encounters the greatest challenge to her self-control, but overcomes it in the end.
Part of the problem with this paragraph is that it is too dependent upon plot summary. Because these incidents occur next to one another in the novel, the writer has put them into the same paragraph; there is, however, no connection made between them. The paragraph begins by talking about the hidden room, and ends with Jane's decision to stay away from Rochester. There is no unity because the writer is merely wandering between events.
The reader has a similar problem when confronted with short, inconclusive paragraphs. As an example, these two paragraphs would read better had they been combined into one:
The ball takes place in a secluded abbey, and the Prince has locked himself and his guests inside the grounds. This setting suggests that everyone in the story is hiding from reality. The locking of the masqueraders behind cold iron gates creates a harrowing sense of doom.
The abbey's structure and its adornments also have an eerie effect on the mood of the story. The fact that the Red Death kills all the people from all seven chambers suggests that it is killing all of the seven seas and the seven continents; it is wiping out the planet.
Both paragraphs discuss what the abbey represents in Poe's "The Masque of the Red Death," but the two observations are too sketchy to stand on their own as paragraphs; they should be part of a single paragraph about the abbey. The problem is probably caused by the lack of a tight topic sentence: the paragraphs are about Poe's use of suggestive symbolism, but instead of a sentence that focuses the discussion, the first begins with an undirected narrative sentence. The effect on the reader is of reading notes rather than an essay.
As this example shows, the first thing you must determine about each paragraph is its focus. Once you have done so, you should never allow yourself to veer away from that governing idea.