A paragraph is a unit or "chunk" of meaning. A paragraph usually contains five to eight sentences, each of which contributes to developing one central idea.
The way you organize your paragraphs will have a major effect on your reader, strongly influencing how easily s/he will be able to move through the ideas in your paper. This is because readers "chunk" ideas when they read. Most readers cannot easily remember all of the details in a written piece, but they can remember larger units of meaning and connect them into a logical whole. Those larger units of meaning are your paragraphs.
Your paper will feel organized to your reader if each of your paragraphs
Revising Strategy: Reverse Outlining
Reverse outlining is a great way to assess how you've organized your paragraphs after you've written a draft or even part of a draft. To reverse outline, note down - in outline form - the main idea of each of your body paragraphs.
If you can't easily identify the main idea of a paragraph, that means the paragraph needs some work - it may need a clearer focus on one main idea.
If you notice that ideas are repeated in different parts of the paper, you may need to move ideas around.
For more information on effective paragraphing, check out the Purdue University Online Writing Lab (OWL). Use "paragraph" as a search term and you will find the essential information about writing well-formed paragraphs in English.