Because words are organized into sentences, sentences into paragraphs, and paragraphs into the finished product, start with your sentences. Make sure that they are grammatically correct and that they say what you want them to say - and don't say anything that you don't want them to say.
Paragraphs composed of nothing but grammatically correct sentences are a good start. But your paragraphs also need to be organized. Typically, the most important sentence is the topic sentence, in which you identify what will be discussed in that paragraph. The balance of the paragraph is devoted to articulating, defending, explaining, or describing what you announce in your topic sentence.
Mistake: There is a golf course nearby and the pumps were plugged in at the time of the house inspection. Mr. Olson informs me that he did not mislead you about the need for sump pumps on the property. We are not really sure what this litigation is about. Mr. Olson put the pumps in after spring rains one year and did not conceal this fact during the inspection.
Better: We are not sure what this litigation concerns. First, Mr. Olson did not mislead you about the need for sump pumps on the property. Mr. Olson put the pumps in and disclosed this at the time of the house inspection. Moreover, they were running at the time of the inspection. Furthermore, the golf course is clearly visible from the property.
The first paragraph meanders through events that are not obviously connected. The second paragraph starts with a topic sentence that tells you exactly what the issue is. The other sentences defend the claim made in the topic sentence.