There is no set form for perspective essays, though they typically adhere, at least somewhat, to the standard essay format. This format includes an introduction, where the writer grabs the reader's attention and offer a glimpse of the content to follow. The body is where the writer offers support for the opinion or thesis given in the introduction. Lastly, the conclusion reiterates the purpose of the essay.
When writing a perspective essay, choose a topic in which you are interested. This will ensure your perspective is easily identifiable and make it easier to write a compelling piece. Do not rely on the opinions of others to support your view -- a perspective essay is explicitly meant to express your perspective, not that of another.
Another purpose of the essay, beyond expressing your opinion, is to help readers understand how you have reached the opinion. The essay must be accessible to all readers. If the topic of your essay involves a technical aspect, do not use jargon that average readers would find confusing.
You will use the first person ("I") when writing a perspective essay, since the opinions expressed are attributable only to you. To add interest to your essay, use plenty of details and examples to illustrate your point.