* Unity: All sentences in a paragraph should relate to a single, controlling idea (the topic sentence). Every sentence should support and develop that main idea. Anything irrelevant should be omitted.
* Coherence: The sentences within the paragraph should be logically connected and flow smoothly from one to the next. The reader should be able to easily follow the progression of thought. This is achieved through various techniques like using transitions, pronouns, and repetition of key words or phrases.
In short, a well-developed paragraph takes a single idea and explores it thoroughly and logically, leaving the reader with a clear understanding of that idea.