Know Your Audience
There are a few issues you should keep in mind as you think about how to write for your audience.
'What is the reader's position with respect to you?' Is the reader your boss, who expects a professional, flawless report? Or a friend whom you can address casually? Given that you'll probably most often be writing for an instructor, consider that you'll be trying to show what you've learned and display your best writing techniques.
'What is the reader's perspective?' Does your reader have a particular role or position that makes him or her biased about the topic that you're writing about? You'll need to take your reader's perspective into account in order to be truly persuasive.
'How much does your reader know about your topic?' Will you need to define basic vocabulary terms and explain certain processes, or are you writing about a topic that will be easily understood by your reader?
Apply Rhetorical Skills
Identifying and recognizing your purpose and audience are important steps to take as you figure out how you'll write about your subject. In other words, these things have bearing on your rhetorical skills and your rhetorical approach.
Your tone in a piece of writing is essentially the attitude that you convey. Will you have a serious tone, a lighthearted tone, or a sarcastic tone? If you're writing a persuasive paper, would you use a scornful tone, sharply criticizing anyone who holds an opposing viewpoint? Or would you have a more respectful, deferential tone, acknowledging opposing views while asserting that your points are the most sensible ones to adopt? (Take note that a respectful tone is typically a good one to strike in your academic essays.)
Consider the two following short persuasive passages:
Passage 1: Our high school has to purchase more computers. Computers are machines that can be used as word processors or for many other technical purposes. Other schools in the area have more computer labs than our school does, and their devices are newer and in better shape, but apparently our principal isn't concerned with whether students have access to current technology. Any funding for the drama department is a waste when we have such outdated computers in our labs.
Passage 2: Much of modern society and business revolve around rapidly evolving computer technology, making it imperative that students learn how to work with computers early on in order to be prepared for the job market later. Our school's computer equipment is severely outdated, so our students are prevented from learning how to use current technology. While there are many valid competing interests when it comes to the school's budget, the school should purchase new computers before spending money in other areas.
The second passage demonstrates much better rhetorical skills than the first one does. The problems with the first passage range from not acknowledging the audience's level of knowledge to being sarcastic instead of displaying a genuine intent to persuade. While blasting an opposing point of view may feel satisfying for a writer who feels passionate about his or her topic, doing so will likely only alienate readers rather than convince them.
The second passage demonstrates better rhetorical skills and would be more effective at persuading the reader to adopt the writer's point of view. The writer has adopted a respectful tone to show that he or she takes the subject matter seriously and has worked to avoid alienating or offending the audience. The passage sticks to offering convincing evidence in support of the main point rather than wasting time defining terms that would be easily understandable to the audience.
Your reader may not always be this excited, but the better you are at employing appropriate and effective rhetorical skills, the better effect you'll have on your reader.