Here's a simple technique to save you time and provide a great service to your readers.
Think 'State and expand'
Make a list of the key points you want to make in your email, letter or report.
Now turn those key points into sentences and use them to start your paragraphs. Think of them as headlines for short articles.
Next, write what your reader needs to know about each key point. You'll be expanding, maybe adding details, evidence, qualifications. Make sure that everything you write in the body of the paragraph supports the opening sentence, or flows naturally from it. If what you are about to add doesn't fit, maybe it isn't necessary or would be better in another paragraph.
One sentence paragraphs okay?
There's nothing wrong with an occasional one-sentence paragraph. You may have nothing to add or you may want to make a key point stand out. Just make sure that your text flows.
Use state and expand and your readers will be oriented whenever they start a new paragraph. They'll also be able to summarise their reading by reviewing all your opening sentences. Your state and expand format will make your key points more memorable.
What about the web?
State and expand is not so suited to the web. Assume that your readers are about to scan down the left of the page after they have read the top line - an F shape. Set out to keep them engaged.
You need plenty of variety. Make it chunky. Create white space with one sentence paragraphs. Use subheadings.