Structure each paragraph as PEE: point, evidence and explanation. If you follow this structure each paragraph will be clear and easily understandable. Each paragraph can be pretty short if you do this right, saving time too. The point should be summed up concisely in one sentence, followed by two or three facts which back up that point and finally an explanation of how those facts relate to the point. The last sentence of each paragraph should some up your point again, so it cannot possibly be missed!