Some universities and colleges dedicate entire classes to the business writing process but the basics are easy to learn. A good professional business letter grabs the reader's attention, lets her know why she should care about the issue at hand and ends with a specific call to action. You want to keep the tone professional and polite. Humor is generally avoided because it can be misinterpreted. You also want to be precise and concise. Avoid generalizations even if it means doing a little extra research before you write.
Clearly identify your audience and tailor the information to their needs and wants.
Outline what you want to say. Organize your thoughts and create a rough draft before writing your final paragraph. Also, consider how this particular paragraph will fit into the letter as a whole.
Write a topic sentence. This first sentence should give the reader a preview of what is to come. Use the outline you created in Step 1 to pinpoint the most important information.
Write the body of the paragraph. Work in all the relevant information you outlined in Step 1. The body of a paragraph in a professional letter is traditionally three to five sentences long, but use as few or as many sentences as needed.
Format your paragraph. If you are using a block letter format, do not indent the start of the paragraph. Instead place a line break or blank line between each completed paragraph. For a traditional layout, indent the beginning of the paragraph five spaces or approximately 1/2 inch.