The components of a good paragraph are a topic sentence that introduces what the paragraph is going to be about, body sentences that explain the idea of the paragraph, and a concluding sentence that sums up what was said and transitions the paragraph to the next paragraph. A single paragraph should consist of ideas that all go together.
A good paragraph, especially for a research-based piece of writing, includes pieces of evidence and explanations of those pieces of evidence. These pieces of evidence can be quotes from a source or statements that back up the argument being made in the paragraph. The paragraph should also have good content. There shouldn't be any unnecessary repetition or information that doesn't relate to the topic being discussed. A good paragraph should also be coherent. The ideas should flow in a logical manner to make it easier for the reader to follow. A good goal to shoot for in paragraph length is about five to six sentences, but that length isn't absolute. A paragraph can be as long as it needs to be, but if the paragraph is getting too long, it should probably be cut up into multiple paragraphs to make things a little easier on the reader.