According to Global Post, a well-written paragraph has a clear and concise topic sentence or controlling idea, logical flow, smooth transitions between thoughts, and a concluding sentence that summarizes the paragraph. Additionally, paragraphs must contain relevant information that pertains to the topic laid out by the topic sentence.
All sentences in a paragraph should support and give additional details about the topic sentence or controlling idea, says Time4Writing.com. The paragraph should also be free of frivolous information and needless repetition. A change in thought or direction requires the addition of a second paragraph with a separate controlling idea or topic sentence.